Poor Service

My mother's fon was stollen we tried to call Cel C to block the Sim and do sim swop,l was shocked to hear my mother's information was not found in the system.Cel C told us to contact rmcs and this company is not answering the calls l waisted so much airtime no one is picking up the calls even if we send mails no one is answering at all.Their Service is poor and l don't understand why are they in charge with the sim cards instead of Cel c