Can I sue for work done improperly?... or least for an adjustment to what was refunded?

Recently, I hired a local landscape company to perform some work, mainly install a wooden retaining wall. After many many phone calls to get someone to show up, one worker finally made it out and worked for a total of 7 hours. The work he performed on the retaining wall was not to standard as there was no foundation dug, the timbers were set wrong, secured improperly, and overall structurally unsound. Soil was actually washing under the wall. After several more weeks of trying to get the man to come back out, I was left no choice to fire him and demand a return of my deposit. I just received a refund from him, with a hand-written itemization, on which he is claiming to have paid his employees $40/hr for labor. Also the number of workers is wrong. Is there anything I can do?

I believe this was his plan from the beginning, and is obviously a dubious business person. Can anyone help me out?