Do you stlil have balance on your account? You can check in the self-serve, if need be you may need to make a payment via credit card or visa debit or prepaid voucher.
Have you tried turning the phone off, removing the battery breifly, then re-inserting the battery and turning the phone back on?
There had been an issue before regarding incoming calls, shown on this thread. I had previously been unable to receive incoming calls and fixed it by turning off the LTE in my device.