Appalling service

I have been receiving endless phone calls on an amount in "arrears" that I have paid for in July, which does reflect on my statement. I have explained myself to many agents and my issue is always escalated and never resolved. My account has now been handed over to a collections company, my account is not in good standing on the app, my card is blocked which I do not mind as I have received poor service from discovery but I really hope this doesn't impact negatively on my credit record as my account is on debit order and the amount was paid. Really frustrated with discovery bank.