Several strategic options come to mind.
1. Respond to all the outraged texts with a link to a not too offensive pritzus site with a confirmation for the first month of service. Guaranteed to stop any further communications.
2. Claim you are the gabbai shaini and blame it all on the Gabbai rishon or
3. Apologize to this apparently chashuvah yid (apparently a legend in his own mind) and promise to give him the Chasan Bereshis aliyah next year, and then figure out how you will explain this to Reb Yankele who already purchased it at the Sisterhood Auction.