I have a galaxy s9+ phone that I got free through the Samsung Insights program. I just tried to switch carriers from t-mobile to at&t. When the person from at&t tried to put an at&t sim card into my phone, it said it was locked. I went to a t-mobile store to try and unlock the phone and they said they have no locks on the phone because the phone was not purchased thru them. When I told them I got the phone thru the insight program, they said I needed to contact samsung to get the phone unlocked. Can someone tell me how to do that please? I am tired of the spotty coverage t-mobile has in my area.