Messed up my credit score for not updating my account for more than a year

i have paid up my debt in 2021, they have my paid up letter, however on my credit report its showed i missed payment with them for over a year... i called over a week ago and they still escalating it... my credit score has taken so long to go up and this is the reason why.... i have asked them to email me the progress, no reply... i have called in numourous times, no futher movement... the have made my life a uphill road after my debt was settled even before they got the account, and now i have a bad record for issed payments and cant do anything as they dont reply or call back, our country went trough hell in 2020 with COVID and all we want to do is get back to our feet, however i problem like this that was not my fault is not allowing me to move forward... :( extremely saddend by ths service