TERRIBLE SERVICE!!!

I received a call to upgrade my contract. Over the call I was explained that my existing airtime would remain only the contract would upgrade immediately with new monthly fee. Over that call was also explained that I can continue to load airtime to my sim like I did previously. However now my sim does not allow any airtime load. Obviously its a **** to get people to remain with Cell C whereas the service is extremely poor!!! No consideration at all for customers. A whole lot of lies was spoken to me I now have a sim that I cant make calls with because Cell C has consultants that have no idea what they are doing! I was promised to be called back for my query...no-one has called me as yet!!!.