How to Get a refund on Fizz when i am still in 15 days trial ?

Details here.
https://fizz.ca/en/faq/unsubscribe
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Cancelling during the trial period
Issuing you a refund is an essential component our trial period. The trial period is 15 days. (This excludes customers who have an approved Proof of disability form; the trial period is 30 days).
Trial period refunds apply only to your monthly fees. Additional expenses such as Add-Ons, Travel Add-Ons and usage purchased with your Wallet will not be refunded.
To receive this refund you must not have exceeded:
The trial period: 15 days for everyone, with the exception of customers living with a disability (who have completed the disability form)
50% of the data included in your monthly plan (unless you have an approved Proof of disability form)
To close your plan during the trial period, use the same process detailed above (with or without keeping your phone number). If you meet the above criteria, your cancellation request will be activated immediately — you won’t have to wait until the end of your payment cycle and your refund will occur automatically.
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If you want the refund, make sure you still have half your data (don't get too generous).

You can remove the credit card from your account and contact Fizz support to confirm the cancellation. They should be able to let you know expected processing/timing for your refund.

Hopefully you didn't give away/use more than 50% of your data. You must be at less than 50% data used in order to claim the 15 day refund.