Upgrade does not applies, I had 250mb pending activation, trying to switch it for 500mb but nothing

You will be able to swap them during your next billing cycle.

When an upgrade is in “pending activation” state you won’t be able to change it until it has been applied at your next billing cycle. I also made this error as well. To keen to apply the upgrade and then got a better upgrade half way through my billing cycle.
Mike made a good point In previous post that’s it’s alway a good idea to wait until 3 days before your billing cycle to apply an upgrade. Once posted you can swap.
Some info on upgrades and rewards https://fizz.ca/en/faq/what-do-i-receive-my-rewards-program

Hi Sergio
If the slot was never used, and I believe this is your situation, you cannot swap your bonus and you need to wait your next billing cycle. I am alway suggest to apply the bonus 3 days before the new billing cycle.

Therefore, next month when this slot is activated, and you want to swap, click on the new bonus, select the slot and it will ask if you want to swap it.

I believe that the majority of us we had this problem

The additions to your slots will be effective at your next payment