I don't live in TO so I can't answer regarding which provider is best. In Montreal, I'm with Fido (runs on Roger's network) and it works decently in grocery stores but it can of course be spotty but this is particularly in very busy areas like Costco. I work on telecommunications engineering so I'll give some insight on the problem and a half-solution for your condo:
Cell waves have a hard time with concrete, so there often isn't really much you can do about this if your condo is made of that.
One pricy solution is to get a cell extender which involves having an antenna outdoors wiring it to an access point indoors which relays the signals back and forth. This is a very pricey solution though and can have its own issues.
My best solution: use online messaging and calling services (e.g., Signal, Whatsapp, FB Messenger). This assumes your WiFi connection is good though. I feel like in this day most people have data plans so you can communicate almost exclusively with these, just a question of getting people to contact you there instead. But this of course doesn't help with lack of reception in grocery stores or the like, just for places where you might have WiFi connection and not cell reception.