Contract cancelation that was not canceled but upgraded without my consent

I am writing to formally lodge a complaint regarding a contract cancellation request that has not been honored and the continued billing on my account. On 27 November [last year], I phoned Vodacom to cancel one of my contracts and specifically requested that the number be retained as a Pay As You Go number. On the same day, I received a written cancellation confirmation from Vodacom which clearly stated that my final payment would be on 1 January. Despite this confirmation, I noticed last week that I am still being billed for the contract. I contacted Vodacom customer care again to query this, and I was informed—incorrectly—that my contract had been upgraded, even though I never requested an upgrade and have written proof confirming a cancellation. I was assured by the consultant that Vodacom would investigate the matter and contact me. It has now been over a week, and no one has contacted me. This situation is extremely frustrating. When visiting a Vodacom store, I am told to phone customer care, yet customer care is clearly not resolving the issue. I have made every effort to follow the correct process, and Vodacom’s failure to correct this mistake is unacceptable. I have been a loyal Vodacom customer for nearly 20 years, and this level of service is deeply disappointing. and for this i will definitely not continue with any upgrades in the future.