Telus does not have any towers in that area at all. Bell's towers are being used in this case. The nearest Bell tower is right across from the Rogers one close to the intersection of Stoufville Rd and Yonge Street. There is also a Bell tower on the east end of Wilcox Lake next to Bayview.
You can see the locations of the towers here: https://www.ertyu.org/steven_nikkel/cancellsites.html
If you are having problems with reception, you will want to call technical support so that Telus can pass the feedback on to Bell.