Bath Fitter Franchising

I have had a water leakage issue in the shower (living on the second floor of a condo) last three years. I had been seeing the bathfitter commercials so I called them, and they ensured that there would be no leakage problem at all after the bathfitter installed, paid $7000, this happened about 2.5 years ago, my issue has not been resolved. They came and checked the liner, said they dont see any tear with the liner, in the end I called couple other plumbers, both told me that bathfitter installed their liner on my old tile and showerbase was broken and the water is sipping through the drain. I called the bathfitter again, they are just not taking any responsibility at all. They want to see active leaking (dripping) the water. So frustrated. $7000 is my kids' tution.