Not keeping to contractual agreement

I called the customer care between the 15th and 20th June 2015 to cancel a contract. I was then offered a contract of R68 per month x 24 which included BIS. This was a good offer so I accepted to agree to take it. However I received an sms in July stating that my 24 moth BIS contract expired 31 July 2015?? So as of 1 August 2015 my BIS was disconnected. I tried calling the customer care since then and was asked to call back to sales then call back again to after sales. It seems no one can give me answers as to who did the contract with me. I am sure all calls were recorded. Vodacom please assist me. I have been with you for 17 years and this is the first time I am having any issues with you.