Telkom refuse to cancel my contract

The 17 march 2015 i took a contract out for a samsung s4 the battery life was terrible, i took the phone back to the store within the 7 day return policy requesting cancellation or different handset they had no stock so i opted to terminate my contract, since then i have been in to the store 4 times and still no help i am still being charged on a monthly basis for a device i didnt use and still being charged till today , the reason is that a battery is an accessory so i have to replace the battery myself for a brend new handset 2nd reason i found a better deal elsewhere hence i want to cancel when i have been a loyal customer to telkom for 3 years as a prepaid customer , few weeks after requesting the line be cancelled i went to a store to get a contract for another phone which was declined because i have a contract already which i had requested to cancel, all i want is for the contract to be cancelled and my money for the past 3 months to be refunded, i purchased a phone cash as i couldnt get a contract due to being young and a high risk ,