Extending subscription (monthly to yearly)

Hello!

I took a monthly subscription first to see if all features would fit my needs. Since they do, I would now like to switch to a yearly model (or more, I just saw that this was suggested on the forum :-p ).

When I want to do it, the interface tells me that I am already on this plan (I waited for the free trial period to end first, I thought that it was the issue here).

Is there a way to extend it before it expires? If not, is there a grace period when I will be able to upgrade or will the service stop when it reaches the end?

Best regards,
Maxime