Record all calls. Don’t talk much other than denying the transactions and demanding full investigation report and address of vendors where all transactions have taken place and copy of charge slip. Let them say whatever they want to say.
Don’ waste your time with customer care executives, collection agents, recover agents…………………….Their motive is only one: to drive you into such a situation that you pay.
Approach your lawyer specializing in such cases. Issue notice.
Get injunction from court from reporting you to Credit Bureaus.
Finally: You may proceed as deemed fit.