IF it's a legitimate email, call Telus directly first thing in the morning - 1-866-558-2273. I believe sales is open at 7am or 8am. Their website says 9am but I think that's Eastern time zone.
Does the email mention anything about transferring your number? Is there a chance someone knows your passwords? (ie: do you use your Telus account email address and password combo on any other site?)
Apparently Telus did send out a text message previously according to one Track+ user. Most cases when Telus changes or shuts down a service, they usually will include a message in the monthly statement a month or a few months in advance.