I'm facing the same problem with my phone, J6+, bought it in Jordan and when I came back to Kenya I can only use it with WIFI, my sim card is rejected (Regional lock).
PLease can you help on how to proceed so that I can be able to use my sim card?
The first thing you should do is to contact SAMSUNG int he place where you bought the phone (Jordan).
They should be able to provide you with the TWO CODES needed to UNLOCK you SIMCARD.
Before you call, please make sure you have a copy of the original invoice when purshased.
Good luck Jessy and be patient.
One thing i do to avoid regional lock is make a 5min call like is descripted in the box. With an european sim card i call to any free number of the provider to get support abroad and surfing differents choices to get 5min call. Then hang up and insert a local sim card and region lock is eliminated.