I think my client is lying?

if he paid for the ads it is not your responsibility to get people to call, your mistake of using your contact number was probably a wise mistake, at least you know the potential of his ads, but in the end it is his product that is selling and if it is done well in the ad, it is his problem

I don't he is lying.
Using a wrong phone number is a pretty big screw up for someone in your role.

Probably, but how would you know? Never perform a contract based upon unverifiable data or results. You were careless in putting your info on his ads. Quality control was seriously lacking.

Same thing happened to my wife basically, wrong address and phone number. They were nice enough to correct and re-due everything but even a year later. My wife still has clients that tell her they were using the other info(happened to be for competitor) over that time period. Even though she won't due it, I think she should be entitled to compensation for those lost sales.
This guy may not only think that, but is going to do something about it, and going to the extreme is just part of the case he is making.