Paying Accounts but Line Cancelled

I have had a contract with Telkom Mobile for almost a 2 years, when I signed up my contract I gave them all by Banking Details to debit the account. One debit order went off and after that I needed to paying in direct deposit etc. now why did I give my bank details???now with that my account was in arrears, I finally paid Telkom back with no amount owing, In May Telkom Mobile cancelled my account on the 27 April 2015 without my consent, is that allowed???My debits are finally going off after months.