Very bad service

I took out a contract phone with telkom debit order date was and still is the 25th of each month. Because I work for a bank if salary date falls on a weekend I will get paid exactly on that date so in April it was on Saturday they debited the Friday before I had to call them to debit the following Monday but was given an account number to pay cash as they were not able to debit but before I could do so on the 30th debit order went off and that only reflected on their side on the 11th of May. My debit for the month of May didn't go off I did not notice that till an email I received from them now I received an sms that my mobile service will be interrupted in 48 hours if no payment is received and I mean I don't have money now and it's not my fault my account had funds from the 25th of May till the 3rd of June. When I called the call centre to arrange for the payment to be deducted with this month's instalment I was told if no payment is made my service will be disconnected I mean it's not fair it's them who did not debit not that there weren't funds, I have never missed an instalment EVER.