ALL I WANT IS TO CANCEL MY CONTRACT

Its impossible to deal with MTN's call centre!! I dial 808 and wait for 30MINS to speak to a consultant only for him to tell me i cannot go through to the department that will be able to tell me how much i need to pay to cancel my contract. MTN ripped me off, i was supposed to be getting 350mb data every month but i only get 150mb. The guy who helped me last year assured me that i will be getting my 350mb as it was supposed to be part of a promo contract. i never get 350mb but hey i thought i'd live with it. Anyways, now i call 808 on friday the 8th and he says he will send a request to retentions department to sms me the amount i need to pay to cancel my contract, its the 13th already and no feedback!!! I want to cancel this contact. but how am i supposed to when you make me wait 30mins to speak to someone and then never get back to me. and also you people are ripping me off! please just cancel it and you need to discount me because ive been getting 150mb data since inception and not 350mb. dont tell me that my contract only says 150mb, blame the guy at Waterfront branch who helped me and assured me i will get 350mb! really i will take legal action as this is not acceptable!