Discovery Bank *****ing from clients

Even after calling Discovery Bank to enquire about an account I don't know it have never ever used with them, and after them realising that it has not been active for more than 6 years, they have still not shut it down..I am still receiving texts every day saying I should pay a minimum of 1100 and this is affecting my credit scoring. a lady from Discovery called me assuring me they will not be charging me anymore as I stated that I don't want them credit facility and surely afyrrvrealising I've never ever used the facility for 6 years, why are they still billing me? here's some serious ***** happening