Double billing for old contract and new contract

I am writing this as a disgruntled customer.I received an SMS in June that I was due for an upgrade. I then went to 8ta NorthGate Shop 278a Northgate Centre on the 18th of July 2015 to upgrade my contract. The person who was helping me with the contract upgrade at the store was not clear about the billing of the new contract. After the upgrade was done, i then received my statement and the statement showed that my old contract was not cancelled and I was been billed for my old contract and my new contract at the end of August 2015. On the statement, it shows that I have been charged with add-on bundles which is R 349 for 5 GIG which I did not receive, on my old contract this 5GIG data bundles was a promotion on my old contract but been charged on my new contract as well. I have been constantly getting SMSs about my billing which I do not understand. It shows that I am currently owing R 2100 but I only took the contract on the 18th of July 2015. I have gone to the Telkom store at Southgate and the person who looked at my issue said that the Northgate 8ta store people should have cancelled my old contract. When I went to Northgate store, they said they could not help me. <br>