i have unlocked my phone to put a sim card in from another country and now it wont let me use the ph

[AC Question]

i have a samusung galaxy s7 and have left the country i bought it from and come to another country and bought a new sim card. i was told i had to unlock the phone so did that but now it will not let me into the phone despite putting my new sim card in it. so i can not use the phone at all . i serioulsly need some help please