I am planning to leave Canada for a couple of months, and I have a prepaid account. I plan to keep the line active, but to exchange the sim to eSim and to downgrade the package to something minimal.
Is the exchange free on the store?
Then, is downgrading also free, or there is a downgrade fee?
Welcome to the community!
If you want to change from a physical SIM to an eSIM you will have to purchase the eSIM it is not free, you can get more information regarding eSIM here.
There is no fee to change your prepaid plan but once your change your package and it is not available anymore then you will not be able to get it again.