FNB hands over fully paid accounts to debt collectors

I paid an account with FNB in full and received a settlement letter stating as much on 11-03-2021. Today I received an SMS from Revco stating that I have been handed over to them for this account. Now FNB nor Revco answer their phones!!! I want to close my account, but I was not informed that my branch has been shut down and now I have to travel to another town to close this **** down. BUT AGAIN, I do not know where my account was transferred to thanks to a total lack of communication from FNB to their clients. I will NOT recommend this bank to anyone. The number of times I have gone into a branch to change my cell phone number is unbelievable, and yet I still cannot receive a OTP on my phone, it still goes to the old number that no longer exists.