Can someone let me know if a US collection agency must follow Ontario Canada procedures if trying to collect from a Canadian citizen living in Ontario?

Yes, they have to follow Ontario procedures, as they must follow the laws of the land of where you are.

But, how are Ontario procedures different than American ones? I was under the impression they are similar.

There have been agencies(Ithink) calling disguising themselves as Toronto law firms (with Florida phone numbers) and in Ontario, the company must notify you in writing that the debt was handed to collections.

So then just hang up on these “lawyers”.

Wherever you live, you should always communicate in writing, and not on the phone with them.

Thanks a lot. I'll keep this in mind if they contact us again.