Worst service provider

Worst service ever .......started off well when I joined paying the R 250 contract .....I decided to cancel it and upgrade for the R700 deal .......they failed to cancell the first deal .Instead they making me paying for both deal..I tried being in contact for a about a month ..the calls were not going through...the day i decided to cancel.. they decide to call and apologize about the mistake they made ..and promised a refund but till today they still trying to make me pay for a service i never agreed with them even after i cancelled a contract with the company thy still want money yet they owe me about R500