No us phoning

[JimAustin]

Hi, purchased the 15 day roaming plan for text, data, calling. I can text but cannot send or receive calls in the US. Have roaming enabled with full signal with "R" showing. Have LTE on. Shows I am on the AT&T network. Have rebooted phone. Have tried using a plus ➕  before country code and number. Still nothing.  Using a Galaxy S9. Any help appreciated!

[softech]

@JimAustin 

your S9 does not have VoLTE and hence you will need 2G for calls

try to manually connect to T-Mobile first and try to make calls, see if the phone will automatically drop down to 2G.  If fails, still keep it on T-Mobile but change the network mode to 2G and try again