Business ProfileforDr Phone Fix

Came in to rhis business to have my cracked phone screen repaired on an otherwise fully functional phone, 3 months old. Company claimed to repair the phone, they did install a new screen and on site it seemed to work, but since the repair is doesn't connect to certain types of networks, and even when it does connect it always drops or doesn't receive calls. I live in a well serviced cell phone signal area. I cant connect to cell phone providers signal properly. The business admitted an issue with repair, i have emails. They asked me to send it back at their cost from Montreal to calgary, (I was visiting town from Montreal when I cracked the screen) they claimed to have repaired the issue the second time around. They returned my phone to me. Issue still persists, not repaired. $1800 phone now useless as a phone. I have asked for a refund for the original service (close to $500) They have stopped communicating with me since I informed them the phone is still not functioning. I have sent them proof. I'm sure they have it written somewhere they aren't liable for damaging a customer phone but if it isn't stated plainly on a document i signed, i want compensation for my now unusable phone. My local technician is convinced they shorted out something on the main circuit board of the phone. Only repairable with new board. $850+. I should have to pay for the original faulty repair at least. I'm a nice guy, I work in customer service they have done what they can but they should be held accountable to their poor quality of service.