Looks like Angor Property Management is trying to ****** money from its customers

I have been living at my house in a complex in Barbeque Downs for 22 years. On Thursday I get a letter from debt collectors stating that my levy payments are in arrears. It isn't, it was paid in full and ahead of time, and I have the banking statements to prove it. The debt collectors said that I have been using the 'wrong code' when I do my payments over the internet and that the money went into a different account. For 22 years I have been making the payments with no issue. What I don't get is why Angor didn't simply give me a call or drop me an email to inform me of the alleged mistake. No reasonable attempt was made on their part whatsoever. Instead, the assholes at Angor simply handed me over to a debt collecting agency, and I am even liable for the cost of the debt collectors' letter. Angor has washed their hands of this, and won't even speak to me. This is abysmally poor customer service and feels like they're making up schemes to ****** money from paying customers.