i need un locked my phone

Is it a Tmobile Sim and a different carrier branded phone? If that's the case it's Sim locked.

The phone works absolutely fine, you can reset the settings, change iclaud without problems! but as soon as I try to insert a SIM, the system tells me that the SIM card is not suitable

because its an American phone tied to a U.S carrier..they have their own rules when it comes to unlocking. only option you really have would be to see if there are any companies out there that will jailbreak it but just keep in mind that at some point it will more than likely re lock to TMO again.

thank you very much for your answer and for your participation! I used a phone in France, the SIM cards are also French, I bought a new phone and unpacked it myself. everything worked without problems until the last days. There were phone updates before this and there were no problems. I can't understand how this is possible (

unfortunately you more than likely purchased a locked to TMO phone or one that was jailbroken. soon as it received an update it force locked it..unfortunately it now must meet the criteria TMO has in place before it can be unlocked..you said you used it for a year but where? here in the states? on TMOs network?

I bought a new phone a year ago.used it for a year without problems a couple of days ago, after resetting home, the iPhone stopped accepting French SIM cards As Apple explained to me, my phone was blocked by your company.  IMEI 35 280684 44882 2 serial number V7G0FHYWCD Please unlock my phone !