THE WORST!!!!! I HATE THIS SERVICE PROVIDER

I upgraded my contract after seeing a new promotion of two Tap 10 tablets for R250 per month with free 500MB per month and R200 airtime, In July 2016. Vodacom was billing be R316 from that month till March 2017, everytime i log a call with them they close it with resolving the issue, I even went to vodaworld to try and solve this issue to no success. They keep telling their billing system shows i must 316 and when I show them the copy of the contract. I get told that system are not communicating very well. In April 2017 I called the cancellation department to and they told me to pay R3315.76 to cancel the contract but I must wait for an official letter of cancellation before i can cancel the contract. That letter never arrived in my email and instead I got the letter which said my account has been handed over to debt collectors and i must pay R8659.17, which they cannot send me statement of how they go to that specific amount. The contract sim cards have not been used from April 2017 till today 05 September 2017. YOUR SERVICE IS THE WORST IN THE COUNTRY..... YOU DO NOT DESERVE TO HAVE ANY CLIENTS !!!! I JUST WANT TO CLOSE MY CONTRACT AND MOVE ON WITH MY LIFE