Theres no contract and refunds should be issued. Unfortunately I do not know for sure. (There is a glitch with my Terms of Service and I cannot view it).
Perhaps you are jumping the gun and canceling too soon? The majority of Fizz Internet customers seem to enjoy the service. Have you tried any troubleshooting?
Hook up a wired connection to the modem. Run a speed test. If it's below par, then contact Fizz. They should be able to fix this for you. If the speed is good, then it's time to check the wifi.
The Hitron modem supplied by Fizz doesn't have the best track record for wifi. Perhaps you may want to use your own router. Follow these steps: https://fizz.ca/en/faq/how-can-i-use-my-own-wi-fi-router-fizz
You have 15 days to cancel if you used 50% of the service. No contract.