Vodacom taking money after 24 month contract expired and cancellation

I approached Vodacom office in George mall 3 months before my 24 month contract expired in order to give them enough notice that I did not wish to upgrade nor renew my contract. I did this again 2 months before the contract expired. On both occasions I was told I was unable to provide notice in a branch and need to call the Vodacom line, which I did. To make extra sure I emailed them days before my contract was due to expire. The day before it expired I was told there is a month `s notice period and I have to continue with Vodacom for another month. They refused to cancel despite months of advance warning and took an extra month `s subscription despite the 24 months having expired. This is theft and ********! I demand my last month `s subscription refunded or I will lay a charge.