Resigned, resignation accepted and in notice period contractual employee

Working as a contractual employee for a big bank. Resigned and resignation accepted. I have three months notice period out of which two and half months have been served. My performance during the course has decreased. Now reporting authority has put a lien on salary account and asking to return three months salary or not get my relieving letter. He has sent a mail stating I have not reported to duty last 15 days ( which is not true and I have evidence for the same, reporting authority and I have been in same room and meeting on many occasions in the last 15 days ). There is no biometric attendance or any other sort of attendance mechanism for contractual employees. There is movement register which people maintain to get travel expenses reimbursement which I have not maintained for last three months as didn't want to claim. Reporting authority is using movement register to say I haven't worked last three months. I have 11 days left on notice period. No bad blood between my reporting authority and me. I have been humble in all my conversations. Focus on work might have shifted after the resignation. Advice how do I go about it. Haven't spoken to hr as being on contractual role didn't have designated hr person to speak to.