I just bought a phone capable of WiFi calling - Xperia XZ2 Compact. I have the $40 Simply Prepaid plan. I tried WiFi calling using the Digits app before I installed the SIM card and it worked fine. After installing the SIM, I can't get it to work. Sony support guided me to the settings menu of the Phone app to see if WiFi calling appeared, and it does not. They said it doesn't appear when it is not provided by the carrier. T-Mobile support said WiFi calling is not available with Prepay plans. However, their website says it does. https://s3-us-west-2.amazonaws.com/.../2019/459221-Rebellion-Prepaid-PDF_110119.pdf Any ideas how to get this working? Many thanks.