Nimble group falsely claims

Good morning my name is Sithembiso promise k**** I’d number *** I had an account with Mtn in 2020 and it was handed over in 2021 to MBD and I had to settle an amount of R5200 I settled that amount with MBD and they failed to issue the paid up letter,I then received a call from the same account with nimble group saying they will need me to pay R1900 in January 2022, I have been trying to resolve the matter with them I managed to get the paid up letter from MTN but my credit history has still been showing nimble unpaid money, I have called nimble numerous times they keep saying they will investigate the matter untill today,when I called them today they said they will call me back,I do not owe nimble anything I don’t know how they obtained my information they had been demanding money from me December 2021 till this date my contact details is ***.i have all proof if requested.