Do you have a device balance left for the iPhone 7? If yes, that will have to be paid before getting a new device or contract. If no, call Telus for best information on cost of new devices. If you go to their website and choose a new plan, the base iPhone X (64GB) is $600 if you choose to pay $10/mo on your bill. $800 if no additional charge on your bill. The 256GB iPhone X is $200 more ($800 / $1000).
One thing to consider is Apple is releasing new devices in a month or so. The iPhone X might cost less at that time if you can hold out til then.
Watch pricing on phones - as of today, the iPhone X is now $400 up front on a Premium Plus plan. As well, trading in an phone can help reduce the upfront cost by an additional $100 or more, you will need to visit a TELUS corporate store for more details.