Lemon truck purchase help

I purchased a 2015 gmc 1500 from a used car dealer just over a month ago. A number of issues came up and they replaced ball joints after a fight. Before I bought the truck I thought I noticed water stain on the roof in the listing photo and asked but they ensured me it was just a bad photo/shadow and everything was checked and is fine with the vehicle. This has not been the case as we had our first heavy rain and I had leaking all over the inside of the vehicle. When I inspected it before buying there was no sign so I imagine they cleaned it up prior to sale. What is my best option for recourse as the dealer is now avoiding my calls. GMC dealer said about 3,000 to repair. I’m in bc Canada and have filed a complaint with vsa already. The photo is of the current damage and it’s also leaking by the front interior lights.