Removal of default

Good day hello Peter I have a default on my name which was listed by prosperitas, when I call them they say its for my child school fees and the child they talking about it was my step child, I broke up with her mother a year and half ago, they kept on calling me and I've explained to them that she is not my child and I only gave my details as a guardian I did not give them my ID no, I only gave my cell no incase of emergency, I did not signed up for anything that involves me in paying for her school fees and this has affected me in getting a promotion at work and I'm suffering for something that I don't know, can you please help me in removing the default on my profile, acc no for the account I have been handed over for its 3433/8305DT2 My name itumeleng moloto Cell no *** Please your help will be highly appreciated and thank you indvance