@dynamite If you don't know if your phone has VoLTE can you tell us what phone you have. If your phone is set to 5G try changing that to 4G/LTE. If your phone is not VoLTE capable/enabled, then try setting it at 2G and connecting to T-Mobile. The USA no longer has a 3G network so phones that are not VoLTE (voice over LTE) will only be able to make calls on T-Mobile's 2G network which can be hit and miss depending where you are.
