I working night on 20.3.2018 when my phone could not receive calls from others.
i kept receiving messages that I have missed calls but my line was full with LTE. I tried restarting my phone and yet it was still persistent. It went on for about 1-2 hours.
Does it still happen on the next day? Try to insert your SIM card to another phone if possible and monitor.
Another way is to contact Careline Live Chat immediately for further assistance on this -