Billing mess up by MTN

Dear MTN your billing system has really made my resentment for MTN worse. since December, i have to constantly call and query, why you feel my account is in arrears? I was told that the billing changed from December and now I have to pay 20 days after the invoice is generated. I was told that if I want to avoid this, I need to set up a Debit Order, which I did, I elected the 31st for the debit order date, yet on the 22nd of February, you deduct money out of my account. when calling, now one could explain this to me and an escalation was logged, which I still do not have a response too. today, I get another SMS to tell me, if I do not pay R598.02 immediately, my account will be blocked.... MTN, I JUST PAID VIA DEBIT ORDER, WHAT THE HELL. so now MTN is billing in advance.... people get it right please. I don't even expect to get a response on this email and if I do, it will NOT address the issue. -- Kind Regards