I can't change the plan to yearly pay nor cancel it nor switch to another. The chat does not work.

I have the Plan for digital photography 20 GB and want to update from monthly pay to yearly as this way I will be charged the same amount as today.
But I have tried 3 browsers already (Chrome, Brave, Safari) and just getting the errors.
If I try the support chat, I get error as well.
If I try call the the support phone number for Czechia, it does not exist.
Pls help.