WiFi Calling Error ER05 Invalid SIM
I have an LG Stylo 2 that I originally purchased from Walmart Family Mobile (associated with T Mobile, so the phone says "T Mobile" when it turns on, etc.) that I unlocked and now have used with AT&T Prepaid for the last 2 years. I have recently wanted to enable WIFi calling as I don't get a good signal in my new apartment, and I get the ERO5 Invalid Sim card message. I took it to the AT&T store, and they were unable to tell me if the problem is with my phone or with my prepaid plan (the $35/month plan). If I buy a new phone, either through AT&T prepaid or an unlocked phone, would that fix the problem, or do I need to upgrade my plan? Thanks!