Ssda ****mers fix my credit

My Mtn account BA*** was handed over to this company last year and they reached out to me and i arranged payment with them i paid my monthly instalments and kept checking my balance on their WhatsApp account on the 01/11/2024 i checked my balance its was R914.57 and i paid immediately i then requested for my paid up letter and did not get it months went by I requested the letter and to my surprise i was told i now owe 16.78 and i paid again and checked the balance and it showed 0.00 and I requested my letter and they went silent until a rude agent called me this year saying i owe R 3000 and if i dont pay it will mess up my credit and she hanged up . I am sick and tired of this back and fourth i need my credit cleared can barely take anything because this now shows as missed payment!! Ssda Fix this