International unlocking does not seem to be working

[Android Central Question]

hi
I got my S8+ unlocked from Sprint which tells me that it unlocked both domestically and internationally. I checked with another sim card (domestic carrier - USA) and my phone is working with it. So, it is domestically unlocked.
When I put international sim card which is 4G compatible and working in another phone, then my phone is not working for that carrier.
any suggestions?

I have not been able to get much help from either Sprint or samsung

 

[B. Diddy]

Welcome to Android Central! Which carrier is the international SIM card from? Make sure that carrier's network bands are supported by the phone, as listed in the specs here.