Susan, sounds like you have done this before, the court part, so you will be prepared and ready. Like Addy said, send the letter certified mail, return receipt requested, otherwise you have no proof you sent him the letter or, more importantly, and that he received it. Hopefully you gave him a time frame. Can't expect him to stop another job and run over to your house next day. I think usually (in Illinois anyhow) they expect you to wait 30 days to hear back from the individual before you file anything against them.
In my view, if you gave them dimensions, depth, drew it out, or had it marked on the ground, and THEY brought in too small of a liner, then it's their fault. If you made any changes while the build was being done, then be careful. If you have all your drawings, and their estimate in writing, what it was going to include, etc. you will be fine. If the OWNER is the mayor, but he doesn't actually do the work, then he will be very upset with his workers. I'm a little concerned with you mentioning that you hired 2 individuals that they suggested. Sounds like the "owner" didn't want to pay taxes for these individuals, so let you pay them directly. I would be a little concerned about them in this mess. Bottom line, though, is you hired the company to do the work, so the company should stand behind their work. Don't bring in the media yet, don't get that "dirty". Wait and see if they offer to fix the problem. Make sure you speak to the person who came to look at your yard, gave you the estimate, told you what he would be doing, etc. Don't talk to someone else. Go straight to the source.
Good luck!