I bought a prepaid sim card and used it on my android, but i had a problem using it and would like to return it. Is it safe to do so? I'm wondering if it could now contain my personal information since I used it, kinda like a hard drive?

  • That's what the cutter blade on your Leatherman is for.
    – user113614
    Jun 6, 2016 at 8:49
  • No, seriously: What are the risks of someone reusing the card? Unknown. What is the risk of destroying the card (which does and can happen for natural reasons as well)? Card is unusable, cost: 0. So, I'd prefer an unusable card over a wild guess, any day ;) I suspect that the network providers do the same, for the same reasons. Jun 6, 2016 at 8:59
  • "would like to return it" ... You may well find your question is irrelevant. Check the returns policy on used prepaid SIM cards ! Jun 6, 2016 at 10:24

3 Answers 3


A SIM card is used to identify the device to the network. The SIM card contains the secret authentication credentials to identify itself to the device. If you are worried about the SIM card being misused for authenticating as yourself to the network, you'd want to disconnect the SIM card from your account and phone number before disposing/giving it away. Your network provider may have already done so when you follow through the process for changing SIM ownership, deactivating a SIM card, or when registering a new SIM to your phone number, but you might want to double check with your network operator.


This begs one and only one question:

  • Did you manually store any data on the SIM card?

No? Then yes, it's perfectly fine to return.

Older devices, like feature phones, that didn't have a lot of built in storage or had incredibly slow storage would store text messages or phone numbers on the sim card to save what little space they had and keep your things easily transferable. Eventually they realized how dumb of an idea this was and stopped doing it. So unless you have forcibly saved contacts to your sim, or text messages, or your phone is dirt old, then there is very little to no data on the sim card other than what was already on there.


I would never pass on a sim card to anyone, especially with what we know from the Snowden leaks. The SIM card is serialised and you are tied to it for the life of the card. If the SIM card is ever used for malicious intent (or at least something the powers at be might deem interesting) it is tied to you.

The worst case would be if the SIM card ends up in an IED, there would be a link between you and the IED.

  • Why would this answer be marked as "not useful" ? I understand that it doesn't address the question about the data stored on it, but the the question was "Is it safe returning or giving away a sim card you already used?". In my town a capital crime was solved because they recovered the sim card out of a burned out car, the murderer had forgot his cell phone in the car when set fire to it. Jun 29, 2016 at 11:16

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