Cancellation of contracts.

Good day. I would like to write this complain. Last year July we contacted Vodacom to cancel our contract. We have send the quotation back and paid within one day. January came and we received this huge bill. We have contacted Vodacom on numerous times as well on Facebook. Everytime just a promise that this will be handle. After the last conversation they converted all our phones to prepaid but we cannot do anything. We still receive an acoount and we will not pay until our contract has been cancelled and the credit paid out to us. We have been patiently waiting on a respond but nothing yet. This is unacceptable.