Nimble Group is a *****!!!!!

I settled the Account back in January 2021, to my surprise Nimble group is harasing me with calls and SMSes to say I still owe them. When I try to call to explain that I settled the account ,they all give the same excuse that they are investigating my case. Honestly if I paid the lump sum what is there to investigate when I even sent the proof of payment?PLease remove my name from your system stop charging calls fees when I have paid!This is affecting my credit score !!!!!!1