this is the full guide https://fizz.ca/en/faq/how-do-i-unsubscribe-from-fizz-home-internet
Important: You have 15 days following the date you unsubscribe to return your Wi-Fi modem, or else you will be charged the amount of $225 (plus applicable taxes). Detailed instructions will follow.
How do I return my Wi-Fi modem?
Mike explained it perfectly.