Not registered on network

Since the update on 15 March I cannot make/receive calls or send/receive messages. It tells me "NOT REGISTERED ON NETWORK". I did a SIMswap and it still does the same. I have tried re-inserting the SIM, switching the phone off and on - you name it. I then put the SIM card in another device and it works perfectly. I need to be able to make and receive calls for my work. How do I fix this???

Welcome to Android Central! Which phone? Have you asked your carrier about this?