Poor Service and deducting money without permission

Currently I have 2 x contracts with Cell C, One on my private phone and one for date (Modem). The Data modem expired early this year and I phoned to cancelled it for end of June 2018. As proof I still have their SMS that states" ********** 101> Your cancellation request was successfully and your contract will be terminated on 30/06/2018. Date of this SMS is 17/05/2018 at 10.54. After end of July 2018 they deducted over R900. from my account. I phoned them on Monday 02/07/2018 and enquire why the deducting money from my account as my account was stopped. I received the following SMS at 13.02 " We have received your query and will attend to it shortly. Your reference no is ********** 274. An SMS will be sent to you when your query has been resolved. Cell C" needless to say they did not call me or sent an SMS. On Wed 01/08/2018 another payment of over the R500 was deducted from my bank account t and again I phoned them and they told me the following "We have receive your query and will attend to it shortly. Your ref no is ********** 927. An SMS will be sent to you when your query has been resolved. Cell C" Time of SMS 10.47 on wed 01/08/2018. Again no response from Cell C. They informed me that my contract ( ********** 101) was stopped and they can not say why money is deducted as they need to escalate it to another department that I as customer can not contact. Same as with the previous calls they will escalate and nobody call back as they promised or sent an SMS as they indicated. The service of the call center people is very bad and they do not have a clue how to work with customers. I will NEVER recommend Cell C to any other person. I can not wait that my existing contract expire next year that I can move on to a better service provider than Cell C. Service very very bad