Changes made to data contract without my knowledge or permission

At the 28 April and early in May 2018 i had called 143 to cancel my data contract which ended on the 4 May. I was told that i would still be billed at the end of May as data is loaded on the 1st of each month. I would get an sms confirming cancelation. This did not happen. I called on the 28th May 2018 at 11h14 and was told the cancelation was not loaded. I confirmed that i had called. The consultant said she would listen to the calls and the person who assisted me would call back. I was also debted and extra amount as my limit was increased without my permission. I did not request this. Hence, also verifying by the recorded calls. At about 13h30 received a call from Tinaye who admitted to me he had increased my limit in error and i was then billed for the extra data. He confirmed my contract would be canceled on the 31 May. He was also told by his line manager that i would not get a refund. I expressed my unhappiness with this as i had not given permission for the changes and at no time was it discussed with me. I was given a reference number as this would now be escalated. Today 31 May 2018 i tried to phone and confirm the cancelation, after 30 minutes the phone is not answered. I then tried 140 and they can't assist but the data contract is still active. So not only are changes **********ly made to my account, my bank **********ly debted and now no one is answering the phone. Service from this department is appalling.