You should contact Fizz, if they owe you money they will reimburse you.
To contact Fizz, click on the link below and make sure you're logged into your Fizz account. The bubble chat will appear at the bottom right corner.
Business hours: every day from 8 a.m. to 9 p.m. (EST)
If you have indeed cancelled you Fizz plans (double check any Fizz accounts you created to make sure they're all gone) you can always get your credit card company involved and ask for a charge back. Call the number on the back of your credit card and make sure you have confirmation on hand that your account with Fizz was cancelled in case they ask for proof.
A charge back often gets quick attention from vendors and service providers...