Citibank — cibil score

I had city bank card.[protected]
We were not receive bill timely, even then i paid and settle all the amount of pending bill except penalty (2900/ rs)
But city bank had send me the bill continuously.
After some time bank says me pay penalty amount 2900/ so that we will not report to cibil,
Again i paid penalty amount but bank damaged my cibil score.
In indore city your bank had closed their branch and they are not pick customer care number also.
Please suggest me what i should do with this case and improve the cibil score

Regards
Manmohan singh tuteja
[protected]