Vodacom Contract *******

I discovered that Vodacom continues to bill me monthly for a contract that has expired. To make matters worse I called them to cancel the contract about a week ago. Was told the system was off-line and they would call me to sort out the cancellation. Nobody called me the entire week. Today I called again to cancel the contract and was told Vodacom require a 30 day notice to cancel contracts. This is highway ******* and I am getting the feeling they delayed calling me back so they could charge me for another month