As the title says. If you have a prepaid SIM (mine is T-Mobile Connect), as soon as you arrive to a foreign country and turn on the phone you will find that it does not connect to any carrier. So far this is normal behaviour. Roaming does not exist in prepaid.
The problem is that as soon as T-Mobile detects you are outside the US it will block Wi-Fi calling. The phone will connect and show T-Mobile Wi-Fi, but all calls will be blocked and you hear a recording saying “your wireless carrier does not allow calls to the number you have dialled”. You can call 611 though and send and receive texts over Wi-Fi calling.
Because Wi-Fi calling is not roaming and it does not connect to a foreign cellular network, would T-Mobile please charge this awful behaviour?