Unethical practice

you should have give him a denial of this notice, and get his State Bar Registration No. and file a complaint against him with relevent documents.

Dear Karan,

You can approach State Bar Council complaining professional misconduct, provided you have strong evidence to prove your allegations.

Send him a Notice asking him for the full details of his claim

Also ask him  The Number and the Court in which he has filed a suit . Also ask him to provide FULL COPY of the SUIT with all the annexures , if any , and also with the notings of the Court Order in which the dates and the directions of the Honble Courts are noted . It will give you an indication at which stage the suit is .

Also ask him the copy of the Power  (duly verified by the notary ) and also ask him to state on oath that  the Power is TRUE and Signatures of the Applicant are original  and You (the complainant) has signed it before him .

Also write to him that if You dont  get a reply within 15 days , the matter will be reported to the Bar Council and a case will be filed against you of forgery and misconduct by a LAWER or ADVOCATE which is bringing shame to the profession

I feel and hope this single letter will solve your problem 

Further , report here and we will see

in addition to what Mr godbole stated asking for his regn no will also be more useful.  Since you never asked him to file civil suit he has no right to thrust his services upon you. He could not have file any suit without your signatures.