Improve coverage, data bundles, etc. with a dual SIM phone

Dual SIM iconsDual SIM phones traditionally provide two lines with a single phone such as for personal and work numbers.  They are also brilliant for prepay users to combine the benefits of two mobile operators or even with two SIM plans on the same operator.

Depending on the combination, this can either reduce data or call costs or improve network coverage compared to what’s possible with just one prepay SIM.  It can also replace a MiFi (mobile router) by using the second SIM slot for data-only SIMs.

How a Dual SIM phone works

Dual SIM diallingDual SIM phones provide the ability to make and receive calls with both SIM cards.  When placing a call or sending an SMS, the phone will provide a SIM choice as shown on the right.

Data connectivity is generally provided by one SIM slot only with the other SIM being limited to calls and texts over the 2G GSM network.  The SIM that will not be used for data will require 2G coverage, which all the networks in Ireland provide.  For example, Three in the UK does not operate any 2G GSM masts, whereas the Irish Three network provides 2G coverage using the former O2 network’s GSM masts.

Some phones such as the OnePlus 2 allow the user to choose which SIM slot to use for data, ideal when using two SIMs that provide a data allowance.

Choosing the SIM for calls & texts

To start off with, I recommend choosing a network provider that will provide right calls and texts plan for your needs, ignoring any data requirement.   For example, do you make lots of calls or need good call coverage?  The following examples are based on Irish network operators with their prices published at this current time (28th March 2018):

Vodafone only coverageCoverage – The Vodafone network seems to provide the most widespread GSM coverage in Ireland.  I have been in various rural areas that a network search only listed Vodafone.  Even some villages such as Carrick (Co. Donegal) only have Vodafone coverage as shown on the right.  The virtual network operator Post Mobile operates on the Vodafone network.

Unlimited Calls – Eir (formerly Meteor) provides unlimited any network calls (mobile + landline) for €10 per month on prepay (Simplicity 10 calls).  Their GSM coverage is reasonably good and I had fewer issues with dropped calls than when I was with Three.

Unlimited calls & texts – Vodafone provides unlimited any network calls (mobile + landline) and unlimited texts for €20 per 28-day interval on prepay.  This Chat Extra plan includes 1GB of data, great for filling in areas without Eir or Three data coverage.

Low cost mini bundles – Post Mobile provide three call bundles – €3 for 35 minutes, €5 for 75 minutes and €10 for 150 minutes.  Their text bundles are priced for the same number of texts.  These bundles last 60 days, ideal for light usage without paying out-of-bundle rates.  They operate on the Vodafone network, offering the same great GSM coverage.

Cheap calls & texts – Lycamobile provides a 450 SMS + 450 minutes bundle for €9 per month on prepay (Talk & Text S).  Their €15 Ireland Plus bundle provides unlimited SMS and calls plus 15GB of data.  While they also have data plans, the speed is reportedly poor and they block tethering.  This is where a second data SIM can overcome those limitations!

Cheap international calls – Both Tesco Mobile and Lycamobile provide very low cost international calls on prepay with many countries priced from 1c/minute.  The main complaint with both networks I hear is the lack of 4G coverage, which again a separate 4G capable data SIM will overcome.  Both providers operate on the Three network.

Choosing the SIM for data

With the right SIM chosen for calls & texts, now you can choose a SIM that will be used for data only.  This can also include mobile broadband SIMs, which generally cannot be used as phone SIMs due to their inability to make or receive calls.  Not a problem with a dual SIM phone, where the SIM will be used for data only.

Lost cost data – Tesco mobile works out at €6/month for 5-10GB using a combination of top-ups and bundle purchases.

  • First month: Top-up by €15, which provides 10GB for 30 days.
  • Second month: Purchase a 10GB add-on from the credit, which provides 5GB for 30 days.
  • Third month: Top-up by €15, which provides 10GB for 30 days.
  • Months 4 & 5: Purchase a 10GB add-on from the credit, which provides 5GB for 30 days.

This works out at €30 for 5 months, €6 per month.  Unforunately, Tesco only provides 3G access and uses the congested Three network.

Update 22nd March 2018: Unfortunately, Eir (previously Meteor) no longer offers a 180 day pass.  Their 50GB pass for €30 now only lasts 30 days.  Previously, their 180 day pass worked out at €5/month for 4G data.

Coverage – Vodafone seems to provide the most widespread 3G and 4G coverage, but at the same time is frugal on its data bundle offerings.  PostMobile operates on the Vodafone network, but with 3G-only access.  They provide 500MB for €3, 1GB for €5, 3GB for €10 and 6.5GB for €20.  Vodafone prepay provides 1GB for €5 or 5GB for €15 every 28-day interval.  This can be useful when combined with Tesco Mobile and Lyca to get 4G as well as much better data coverage.

Roaming – Three UK’s data SIM plans include free roaming in a wide range of countries.  These SIMs can be easily obtained from Amazon or eBay.  They typically include 1GB to 3GB data and generally last for one month from their first day of use.  Another option would be to get a local SIM of the country you intend visiting.  Check the airport arrivals area after landing and the shops for any selling prepay SIMs.

Note: When using a mobile broadband SIM, check that the phone uses the correct APN for this SIM.  Some phones automatically set the phone APN, which may not work or could result in out-of-bundle charges, especially with Vodafone.

Tip: See this article for tips on forcing the data SIM to stay in 3G or 4G mode.  This does not affect second SIM slot, which will remain in 2G mode.

Other combinations

For some people, they just need something extra that is missing on their primary SIM, such as cheap international calls.  By keeping the primary SIM with a dual SIM phone, this does away with hassle of switching networks, particularly if the existing network is fine for everything else.  This lets the user freely switch the second SIM without affecting the ability to receive calls and texts on the main mobile number.

OnePlus 2 default SIM settingBest of everything – Consider Vodafone’s Unlimited calls & texts prepay plan as the primary SIM, which includes 1GB of data for €20 per 28-day interval.  For light data users, this will provide the best coverage for calls, texts and data.  For cheap International calls, use Lyca or Tesco Mobile for the second SIM.  If you run low on data, switch to the second SIM for data – a 1GB add-on costs €3 on Lyca or €5 on Tesco Mobile.

MiFi replacement – Insert the data SIM into the second SIM slot and set it as the default data SIM.  Then enable the phone’s Hotspot to connect your laptop or tablet on the move.  The phone will also use this SIM for its data.  This feature is best used with Eir’s prepay mobile broadband 50GB plan.

Some dual SIM examples

The following are some examples of combining the features of two SIM cards:

Mini call/text/data bundles – €15 per 60-day period (€7.50/month)

  • 75 minutes (Vodafone coverage)
  • 75 texts (Vodafone coverage)
  • 1GB 3G (Vodafone coverage)
  • Cheap international calls (Former O2 coverage)
  • SIM 1: PostMobile 1GB data, 75 texts and 75 minutes add-ons.
  • SIM 2: Tesco or Lyca (No bundle, for cheap International calls)

Large call/text/data bundles on a budget – €15 per 28-day period

  • 450 minutes (Former O2 coverage)
  • 450 texts (Former O2 coverage)
  • 5-10GB 3G data (Former O2 / Three 3G coverage)
  • Cheap international calls (Former O2 coverage)
  • SIM 1: Lyca €9 Talk & Text S national bundle
  • SIM 2: Tesco €15/top-up or €10 5GB add-on (~€6/30 day)

Big bundles with Vodafone call coverage – €26 per 28-day period

  • Unlimited calls (Vodafone coverage)
  • Unlimited texts (Vodafone coverage)
  • 5-10GB 3G data (Former O2 / Three 3G coverage)
  • 1GB* 4G fill-in coverage data (Vodafone coverage)
  • SIM 1: Vodafone €20 Talk & Text with 1GB data
  • SIM 2: Tesco €15/top-up or €10 5GB add-on (~€6/30 day)

*Note: Switch to the Vodafone SIM when you need data in a Eir data blackspot or faster speed.  Don’t forget to switch back afterwards!

Big call & data bundles with cheap international calls – €20 per 30-day period

  • Unlimited calls (Eir coverage)
  • 15GB+ 4G data (Eir coverage)
  • Cheap international calls (Former O2 coverage)
  • SIM 1: Eir €20 calls & data simplicity plan
  • SIM 2: Lyca or Tesco Mobile (1c/min to many countries)

Update 6th April 2017: Vodafone increased its phone data bundles to 1GB for €5 and 5GB for €15, both which last up to 28 days.  I updated the above text where these figures were mentioned.

Update 22nd March 2018: Eir reduced the 50GB prepay broadband bundle from 180 days to 30 days.  Revised the above sections with alternative options.

2 thoughts on “Improve coverage, data bundles, etc. with a dual SIM phone”

  1. Great article, very interesting indeed , I appreciate all the time that was put into it ,
    Have you thought about an lte home router

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