About to loose my job cause cell c ****med me 10k

I've had a cell phone contract with cell c which was handed over to Nimble collections services,the balance was 10k Cell c black listed me, when nimble bought over my debt they also black listed me, I've fully paid nimble and they gave me the paid up letter and removed the listing they made but the one cell c made is still black listed, nimble is saying they can't remove it cause it was listed by Cell c

It's been months since I paid it off but am still black listed, I can't uterlise any credit facilities, worse I work for a Financial services provide specifically a bank and am not allowed to be blacklisted, as we speak my job is on the line and am not understanding why am still black listed after I've paid cell c off the full amount I was owing, anyone with how I can get assisted please assist me cause they always promise to contact me since beginning of this year and I've never been contact by cell c since, they just say they'll contact you for capturing reasons but they will never contact you, I've explained several times that am about to loose my job but they not giving a damn, cell c has ruined my life completely ,imagine I've paid 10k but they not willing to even contact me and assist me