In my account, it says it is not possible, and I have to wait for one month. But I should do it tonight because I need it for the next month.
Unfortunately you can’t anymore. There is a cut-off time (48 hours before the plan renews)
Important – any change to your plan must be made 48 hours before the end of your payment cycle. During those 48 hours, systems are frozen and no change can be made. You’ll therefore have to wait for the next payment cycle. Source: https://fizz.ca/en/faq/how-do-i-change-my-mobile-plan
So I don’t think you can do anything before the next month. If your plan renewal is more than 48 hours away, then it’s a system error and you should contact support.
Sorry, I wish I had better news :(
Sorry but like StefanM said you cant but you can try to contact the support maybe they can help you. Fizz i s a pre paid service so you paid before getting the service.
Have a nice day :)