Almost 2 months and multiple enquiries, still can't make or receive calls

<p>I've been in the UK for a year and bought out my contract. On my return I went to renew my contract in order to retain my old number. I've been told I should do a sim swap and then all will be in order. After about 2 months of paying my contract, 6 phone calls to customer service and 3 case escalations that were "resolved" absolutely jack has changed and I'm still unable to make or receive any phone calls! Highly frustrating!!!</p>