Consultants not geared up to handle queries

My contract is about to terminate on 08/05/2015. I have spoken to a consultant and was told that I had to sent a notification for the cancellation of the contract which I did accordingly. I have phoned back today 29/04/2015 to confirm that the cancellation would be effective on the 08/05/2015 as I need to migrate to PREPAID. Now I am told that this can only be done after the 08/05/2015. I am terribly confused because each consultant gives me a different answer . I am also terribly disgusted with their service as I had to wait almost 30 minutes before a consultant would speak to me. This is really frustrating