1. You clarify the details of outstanding dues to be paid by you to them on the basis of the documentary evidences for having paid all the outstanding amount.
If it is confirmed that you are liable to pay any amount then you can issue a legal notice demanding explanation as well as to remove the tag attached to your name which prevents you from availing further loans.
2. The CIBIL score is based on the report submitted by your lender against you for the defaulted loan amount, hence CIBIL cannot be held responsible for the adverse entries in its records.
3. The lawyer fee can be heard from the lawyer who you would engage.
4. If you suspect their integrity then ignore them and try to fix the issue through your own sources.