I've just switched to virgin from EE (ported phone number across) and I've come across an issue with calls.
When I'm on 4g I am unable to receive incoming calls. If I manually switch to 2/3g I can receive calls as normal.
I've gone through help with the text messaging service and they've not been able to help or at some points even understand the issue. They did issue me a replacement sim which didn't resolve the problem.
Running a OnePlus 5 on the latest version of Android available from the manufacturer.