I see the chat icon right now at 715pm. I believe that the same people that do the web chat also do the twitter help @MTShelps and they have not filed their twitter log out messages yet for the night
The link https://www3.mts.ca/mts/contact+us that Tennille posted gives you all the ways to contact them and shows the status of web chat.
One thing though there are a few pages that I just noticed don't show the chat icon. You have to go down one level to see it.