Welcome to the community!
Unfortunately, Fido no longer offers a per minute plan. That plan would have operated like the more traditional pay-per-use model. However, since the accounts need to be topped-up regularly in order not to lose their balances, customers were accruing rather large balances. The current prepaid offerings require the monthly or yearly plans. There are some other providers which still offer the traditional pay-per-use model. You should note that those offerings also have expiring balances, though the length of time before expiry varies with provider.
Hope this helps 😀