How to unlock used iPhone


    Hello! I recently bought used  iPhones7 by Seller (owner of the iPhone) used T-Mobile USA, but he is no longer T-Mobile customer. He said me that the phone has been paid in full.

    I'm not from USA . I have T-mobile sim from this iPhone (it belonged to original owner). Unfortunatelly carrier T-Mobile doesn't work in my country.

    When I insert my sim card to use it iPhone says "the SIM Not Supported".

    I want to use the iPhone with my local carrier.

    Please can you advise me as to the steps I need to take to use iPhone with my local SIM card.  Could you unlock my iPhone from T-Mobile please? 

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