Account allowed to increase, though in arrears

Account i***-7 - This account has been in arrears for quite some time, I have tried on numerous occasions to cancel the account, but was told that this is not possible. In August this year, I received a new handset as a gift, I immediately transferred my sim card from the Blackberry to the new device - Samsung J1. I was not au fait with the billing of data and the fact that I had to close applications after use. As a result, the bill ran into excess of R3500. I called the call centre and spoke to one of the consultants, I explained my dilemma and the fact that I simply could not afford to settle the account. Surely this should not be allowed in terms of the Consumer Protection Act. If a debtor is in arrears and has expressed this, why was the account not barred and closed off until outstanding payment settled. Disgruntled customer!!