Missed payments

Goodday I don't understand in 2018 I took out a contract by mtn they help me very friendly and I received my phone contact for 24 months. In 2020 my contact expired and I closed the contact, but since that time on my credit score they keep giving me missed payments then I send them emails then they removed the missed payments. On 2022 they help me to remove all the missed payments there was only one missed payment on 2022 may. Now on 2024 January the said again I missed a payment. Please give me advise or help me what can I do to sue mtn for that.