Carriers such as At&t, T-Mobile, Simple mobile, H2o, Red Pocket, AirVoice etc. have a Sim Card slot in the phone. Each Sim Card has a unique serial number, the cellular phone number gets assigned to the Sim Card (using its unique serial number). The assigning of the phone number to the Sim Card gives the user the choice of changing to another mobile phone by removing the Sim Card from one phone and inserting it into another unlocked cellular phone or another mobile phone from the same carrier. (NOTE: If the replacement phone is locked to another carrier or not compatible with the original carrier it will not work!!!).


GSM cellular phones are user friendly meaning the user can just remove the Sim Card from one cellular phone to the other without calling the carrier and having to inform carrier that a change is or going to be made. If cellular phone breaks for any reason or not functioning, Sim Card can be placed in another mobile phone and will operate immediately. Each carrier carries their own Sim Card (At&t will only operate on At&t Sim Card, T-Mobile will only operate on T-Mobile Sim Cards etc).


When buying a cellular phone directly from the carriers the Sim Card is included in the package (also usually means that the cellular phone is locked to be used with that carrier only – most phones can be unlocked).  When buying an unlocked mobile cellular phone the Sim Card is usually not included – since its assumed that you already have a working phone and getting a replacement.


The Sim Card usually stores the contacts of the phone (some phones such as Blackberry, iPhone) on the Sim Card. When changing cellular phones the contact will move with the Sim Card to the new phone. Most cellular phones have a lock code and some users choose to activate that code to stop anyone from just picking up the phone and using it. Sim cards have the same feature, always remember to write the password somewhere (even though you think you will never forget the password – you will…lol). When entering a password always remember it – when entering the wrong password too many times the Sim Card will lock up and a replacement Sim will be needed and you will need to call the cellular phone company to transfer the phone number to the new Sim Card.

Common problems and solutions:


Where is the Sim Card on my Phone?

  •  Sim card slot is usually located on the phone under the battery (Apple iPhone up to 3G models its on top and on the 4G phones its located on the side of the phone – Check on our post for detailed instructions)

My cellular phone says “insert sim” ? 

  • NOTE:  “insert sim” and “invalid sim” are not the same (FOR “invalid sim”  check bellow)
  • Make sure you Sim Card is entered to the slot correctly. (sim card slot is usually located on the phone under the battery)
  • Take out the Sim Card and reinsert. Double check that the Sim card is inserted correctly (most phones have a small picture or indent showing the direction the Sim card should be inserted. (if you do not see the display – get a magnifying glass and look again) 
  • If phone still displays “insert sim”  take out the sim card and wipe the contacts down (do not use any chemicals).
  • Try wiping the contacts for the sim card that are located on the phone (only if  you can reach them. DO NOT insert any objects if you can not reach the contacts – you will most likely do more harm then good)

I have tried all options above – do I need a new Sim Card?

  • Before buying a new Sim Card try inserting another Sim Card into your cellular phone. Even if the sim card is from another carrier and will not work with your cellular phone. If the sim card is reading (even to say that the sim card does not match the phone) you are having a sim card problem.
  • If the replacement sim card gives the same error “insert sim”  it is most likely that the problem is a PHONE problem and not a sim card problem.

Phone says “invalid sim”

  • The cellular phone that you are trying to use may be locked to another carrier.
  • Sim Card may be old and need replacement

I have moved my Sim Card from my old phone to my new phone. My contacts are not in my new phone.

  • Most cellular phones have the option of saving phone numbers to the phone or the Sim card. You may have have saved your contacts to your phone instead of the Sim card.
  • EASY TO FIX – if your old cellular phone is still working and in your possession.  Reinsert the sim card in the old phone – Go to Menu – Contact – Modify – Copy all to sim (you may have another option of merge to sim – if its there use the merge)

I think my sim card is not working – can I use an old sim card?

  • Only if that old sim card has never been activated before. You can call your carrier and have them move your account to that sim card.

Where can I get a new sim card? 

  • Any local cellular phone store (make sure you get the correct sim card for your carrier). 
  • A carrier store such as At&t or Tmobile (each will only have their branded sim card)
  • You can call your carrier to send you a replacement (if you can wait) and (they do charge for new sim cards – usually the same or even more then you will pay at a local store)
  • Online  - The cheapest way to get a new sim card 
Simple mobile offers some of the best rate plans today
Want to move your number to Simple Mobile – you will need a new sim card
Are you selling Simple Mobile service? Buy Sim cards here and save!!!
Do  you have a store and want to offer Simple Mobile?

Once you purchase the Sim Cards and receive your order you can start offering Simple Mobile 

at your location


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BUY H2o wireless SIM CARD HERE

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Shipping within 24 hours – NEED HELP call 718-942-7594



Shipping within 24 hours – NEED HELP call 718-942-7594


BUY At&t wireless SIM CARD HERE

Shipping within 24 hours – NEED HELP call 718-942-7594