Look into the attachments.
Prepare a list all telephone calls received at your end with phone number date, time . Record each call received now onwards and ask the calling person's name, designation, department, name of company (if it is citibank, or collection agency, or recovery agency) address with pin code, official phone number with STD code (if the person is calling from mobile/unidentifiable number) official email id, fax number and RBI registration number if it is a recovery agency. During each call tell them ( while you are recording) that as per full and final payment communication you have paid and now if the company wants any more payment company should supply you a letter under original seal and signature by hand of competent employee along with his/her full name, designation, department, location.
If they are using any coercion (e.g name recorded in defaulters list) threatening, in a abusive rude manner it shall get recorded. Lodge a complaint with local o/o Police Commissioners/SP under acknowledgment, in person, by letter, email and obtain complaint number and mention name and address of all people including MD/CEO, Principle Nodal officer/Grievances Manager Anjana Makkar. If they are coming to your place them hand them over to police.
Meet Local BM of Citibank and obtain the address of local grievance/Customer Service manager/Collection Head/BM of Citibank and make them a party. It shall be better if you can take some influential/reputed people with you and announce to the bank that you shall advice people known to you to close their a/c with Citibank and approach the local media as well.
As per RBI guidelines you can obtain copy of your credit report from the bank by making a payment ( each bank can fix amount but not exceeding Rs. 50/-) of fee fixed by bank. You may submit a letter to the bank with cheque of Rs.50/ only and demand your credit report by redg/speed post within 7 days along with copy of communication of bank ( by email/letter whatsoever) to credit rating agency ( CIBIL, Master Card International Negative List , Experian , Equifax ,etc).
Call Anjana Makkar whose toll free number is given on CC bill and web site and send a follow up email in a terse language, and demand that bank should remove your name from defaulters list from all credit rating agencies and confirm so in writing, supply you FNF payment /NOC, and beg apology in writing so as to reach you in next 7 days by regd/speed post or you shall be constrained to go public and approach the institutions of Police, Courts of law, print and electronic media, social and legal forums, NGO’s, consumer court, consumer forums, Govt. regulators, ministries etc at the cost and consequences of the company.
You can obtain the previous consumer court decisions against Citibank at CONFONET.
You can also approach forum like pehredar, mouthshut etc. The idea is to tame them and shame them.
You may quote a few of them and mention that despite the intervention by law full authorities bank has remained a habitual offender and you shall be constrained to approach the Govt to ban the company. If you are not able to resolve approach a competent and experienced lawyer and your lawyer shall do the needful.
Which city you are located?