Invoice for a Memorandum that I did not authorise or ask for

Hello I had held some ESOP shares of my ex-company which was taken over by a MNC which I was forced to sell for the deal to go through. I just had 0.0001% or lesser holdings. As a part of their due diligence process my ex-company asked for lot of snapshots of my income tax portal and other details which I have provided as part of the take over process. After all the process and money remitted to my account my old company sent me a invoice for Fees for 281 memorandum of Rs.88,500. This more 12% of the total value that I received for my shares! But I was not made aware earlier by anyone nor did I approve for any work related to this service during the take over process. It was the mandate of the MNS company that all scrutiny of the existing shareholders be done by one of the Big 4 audit firms for which my old company agreed for. For me it's nothing more than a waste piece of paper. I did not ask for it nor was I informed that there would be fees involved in doing this nor did I sign any document relating to this service. I just gave some screenshots of certain areas of my IT portal such as pending actions and filed IT returns. I was shocked when I got the invoice from my ex-company asking to pay. I have refused to pay this since I did not ask or signed up for this service. Who is responsible for paying the fees involves in getting this kind of details? I myself provided all the details and they just put all of them together in a PDF. To me it looks like somebody doing a background check on me without my knowledge and then charging me a hefty fees for that. Is it valid? Am I liable to pay for this invoice? Please let me know your thoughts.