Harassing phone calls

In house solutions have harassed me 4 different times in the last 3 years.  The first time I wasn’t educated on fake scam collectors. I had my bank stop the payment when I saw 2 collectors getting money for same bill. Now they have contacted me 3 more times.  I hate that I am a target. I did pay the correct collections department and have a letter paid in full.   They tried to say it was a different account last 4 on cc was different but same company Walmart. Unbelievable I don’t have to prove anything just wish someone with authority would stop them 893-716-8051.  I have 2 other numbers also