Written off account

Last year may I went under debt review unknowingly even before i was put on debt review my account was up today , on monthly fee which they can check from there side. I was cleared this year April but unfortunately my account was written off when full balance on the account was paid and I had received my paid up letter from Trueworths I am stuck with this written of on my account and it's affecting my score and I can't get any credit reason is the trueworths account being written off I still have my paid up letter please Trueworths assist in this regards