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Multiple old questions (here, here, here, and here) document that even when mobile data is switched off, mobile data still gets used as part of 4G voice service. I'm looking for up to date information (e.g. possibly relating to 5G, eSIMs, latest Android version, retirement of 3G, etc.) to see if the following scenario is possible without rooting my phone:

  • Home SIM active for SMS (but not MMS)
  • Home SIM active for voice calls (this is not essential to me)
  • eSIM for ALL mobile data used while travelling

Why am I so keen on this? The ability to receive SMS codes is sometimes needed to verify oneself to a service. (Yes, I know it is not as good as other alternatives.) As of 2023 eSIMs provide very cost effective data service almost anywhere in the world, while international data roaming charges from one's home carrier can be exorbitant (e.g. $10/MB for me). At those rates, tiny amounts of unexpected data use can add up fast.

Doing all of the following is NOT sufficient to avoid use of mobile data:

  • Turn off mobile data AND turn off data roaming for the home SIM
  • Send zero text messages and make/receive zero voice calls
  • Turn off MMS for the home SIM
  • Turn off "Data during calls"

Questions:

  • Are any new strategies/settings available or in development?
  • Does 5G have the same problem as 4G - using data to establish itself on the roaming voice network?
  • Would setting preferred SMS to my home SIM, but voice calls to a data-only eSIM be possible?
  • I would consider moving to iPhone: Is this an Android-specific issue?
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    To my knowledge most 5G networks (not sure about China) are still running in 5G-non-standalone mode which means 5G is effectively just a data booster for 4G but all the management data is transmitted via 4G. It is really a pity that Goggle doesn't manage to fully split voice and data channels so that they can be correctly charged by the MNO (or in your case not charged as there is no traffic).
    – Robert
    Aug 21, 2023 at 19:11
  • A simple solution, you are not using the sim remove it. Aug 21, 2023 at 21:18
  • @RohitGupta It is difficult to know when SIM card (in this case the "Home SIM) is "unused" if it is used for incoming calls.
    – Robert
    Aug 22, 2023 at 7:18
  • @RohitGupta If SMS were never used as part of authentication in any service nor for alerts from my bank, airline, etc., my problems would disappear. Enabling the SIM on the roaming network for even just a moment triggers a whole lot of data traffic. (Physically removing and fully disabling the SIM in settings are equivalent. - no need to fiddle with removing the SIM.)
    – Ian W
    Aug 22, 2023 at 12:55

1 Answer 1

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I think that if you want to receive calls on your normal sim, then you are roaming. You can't have it both ways.

Suggestion. Have two sims (or a sim and esim).

  • First SIM, select a plan that has a phone number and no or low data that stops or slows down when you reach the limit. Or get one with no data.
  • Second SIM, get one with data and leave it off until required.

I have used BNESIM to give me data (it came with a limited phone number that I did not use). You only have to top it up once a year. They now have esims as well. I am not associated with it.

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  • I'm not sure we are on the same page. I do want and use SMS roaming with my 'home' SIM precisely because I need that specific number working for authorization. I do have 2 SIMs ('home' plus eSIM for data when travelling). The problem is that Android is allowing some data use on the 'home' SIM. Changing my number or not having mobile data plan in my home country solves nothing for me.
    – Ian W
    Aug 24, 2023 at 12:49

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