Bad service

I went to the store in Lakeside mall and told them that I want to cancel my airtime contract I have with Mr Price,they could not help me but I was told to call a number because if they call they is always no answer,I tried to call for 3 days now but the phone just rings without an answer....yet if u don't pay,the call center can call 10 times a day,how do I get to the airtime department and cancel this contract?