NO STATEMENT CAN BE FOUND IN THEIR SYSTEMS

I had a cellphone contract with Vodacom for 14 years, and being renewed every 2 years. I cancelled my contract last December 2014 upon the maturity date. Vodacom debited my account end of December 2014, end of January 2015, and end of February 2015 after the contract was cancelled. My phone was then converted to a prepaid as at 01 February 2015., meaning I DO NOT OWE VODACOM A CENT. My last statement received from Vodacom was in January and nothing for February beside the debit order. I continue to use my phone as prepaid with no phone call/ statement/ debit order from Vodacom stating I have a bill to pay. Sudenly VVM ATTORNEYS started calling me in September 2015 to make arrangements of paying my Vodacom account. I went back to Vodacom requesting the statement in CENTURION, there was no record found and they called the call centre none could provide proof that I owe them. Please provide proof that I owe you for what? And if I owe where is the agreement signed that I took your offer? What was the arrangement? And why kept quiet for so long without notifying me about this? Are you absent that I cancelled my contract with you ?