Phoenix ARC Private Limited — Barclays Credit Card outstanding was settled in 2009 but even today it is showing outstanding against my name

Barclays Credit Card outstanding was settled in 2009 but even today some amount is showing outstanding against my name impacting my CIBIL score.
The settlement was done with Barclays Bank whose credit card I used but looks their system was not updated properly and when Kotak took over they starting following up with me for payment and I provided all the necessary documents pertaining to the settlement such as Settlement Letter issued by Barclays Bank, Copy of DD for Rs. 55000/- and then receipt. Every time I submitted such proofs there was no mail communication whether it is updated in the system or not. Then after a pause for few months or some times even years I again receive communication about outstanding payment. Later when Phoenix ARC took over I received similar kind of mails asking for payment. Then I submit necessary proofs of settlement but they never updated the system. There was no mail communication from them since 2016 but suddenly today when I see my CIBIL statement they are showing an outstanding amount against my name. Because of this my CIBIL score is affected. Kindly look into it.