I have the same problem too. Based in the UK and unable to receive or make any calls. Strange thing is that I can receive sms but cannot send out sms. Well, good thing is I can receive Tac when needed for my online banking. Super weird though!

I went back last summer and change my sim as I thought sim was the culprit. But when I arrived in the UK, it works well ie. Can receive call and sms but after few days/month, I noticed the same problem recurring again. Been contacting CS team for many times and unfortunately they unable to solve the issue.