What to do when Cell C does not deliver and refuses to activate a sim card and complete a port??

I would like to know whereto from here, if you have tried to ask for assistance and Cell C still ignores all requests. After a week waiting for a port and sim card activation, Cell C still fails to sort this out. After they have promised to call back, x2 different consultants, but still nothing. Can you return a hand set and cancel a contract if a provider does not deliver and you are unable to use a handset due to Cell C not activating a sim card and completing a port?