Legal action?

The worst experience ive ever had with a mobile service provider. My debit order went off on the 1st of the month but failed because I got paid 1 day late. When I got paid, which was literally a few days after my debit order date, to my surprise Telkom handed my account over to a debt collections company who is wanting me to pay the missed installment plus the one that is due month end only. And when I want to make the arrangement with this company, they dont answer their phone. However, I am receiving emails and sms's threatening to take legal action against me. All this because I missed 1 debit order which I wouldve paid but got handed over to a debt collection company instead. Ive been a customer with telkom for years, and im appalled at the level of compassion. They are literally treating me like a ********. When I call them, the lady just repeated the same thing that ive been handed over so there's nothing they can do. And when I ask to speak to a complaints department or something similar, I was told theres no such department. Then after some time she just muted the call till I dropped the line.