Bad customer service

I am getting R55 airtime from Mr Price every month and I went to them in May to cancel the contract as I was told it can be canceled anytime and I was given an email to cancel and no respond from them since 31May till today. The reason why I want to cancel is because I am paying for nothing as I get airtime and immediately after few minutes the airtime disappeared. I called my serve provider vodacom to enquire or to check if there's anything I have subscribed with and they told me I have not subscribed with anything and they advised me to contact Mr Price about the airtime. Which I did and Mr Price since they said they will investigate till today. So I don't want their airtime anymore as they are unable to resolve my problem.