Paid up account put on "default" even thought i paid the required amount with proof.

I had a month to month contract with Cell C, Which due to unforeseen circumstances couldnt pay during covid times, I contacted them that i wont be able to pay so that they can cancel my contract, they closed my sim card and i assumed things are fine then. Few month down the line i started getting calls from lawyers Hammond Pole to be exact which saying i owe certain amount from Cell C, I paid them and i still have proof of sms payments, Suprisingly on Clear Score its showing that im on default, Please assist with removing the judgement on my name as it is ruining my profile