Frustration with Vodacom service

I called vodacom and told them that i wanted to cancel my month to month billing because its very expensive and i we were not sure of our future plans so we didn't want to sign a contract. So she said i should write letter on letter head and send to the email she gave me. So rather than cancelling the contract they deleted our numbers. This were all business lines by the way. Since then it has been a matter of numerous phone calls and now only 2 of the three are working. The last line which is the main business line which majority of the clients use is still not working. I feel very frustrated because to me cancelling a contract and deleting a number from the system are 2 different things. I was not well informed by the lady i called properly that cancelling a contract will delete the number completely. If i remember correctly i also told her that i will just use airtime prepaid. Its been more than a week and clients are under the impression that we are closed down and we losing alot of business. Am frustrated and i don't know what to do. All i want is all my lines working and they keep saying they having error. Who should i turn to if they keep saying this. We have been their clients for many years and we don't deserve this kind if service. Feeling disappointed and let down.