I have settled my loan account with Tadi loans a year ago , they have given a settlement letter bt they listed me as a defaulter so i can't get a loan or apply for credit anywhere

I have settled my loan account with Tadi loans a year ago , they have given a settlement letter bt they listed me as a defaulter so i can't get a loan or apply for credit anywhere. I called them several times , even escalated the matter to the big bosses at Tadi loans for help but still no help . It affects my credit score as im being listed as a bad payer who's account is at a default status . Can you assist me to resolve this matter with them please.