Permanently (?) unlocked phone: Invalid SIM card




    I bought a T-mobile phone from a reseller in the U.S. which is permanently unlocked (according to them).

    It worked there with my hungarian SIM card, and it worked here in hungary for 3 months until today.

    Today it says "invalid SIM card - Network locked SIM card inserted".

    I've tried to factory reset my phone and also tried the - "Device unlock" application, but it says "Service not responding. Please try again later.".

    What can I do in this situation?


    Thank you in advance

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