Can i change webinar plan from 500 users to 100 users?

Hi!

I bougth Zoom one pro for one year for meetings with my students. But i also need zoom webinars for maksimum 100 users. I can buy Zoom webinars for 500 users. I really don t need so big room for my webinars. Why i havent got options to by smaller webinars? I feel that i am throwing money way.

Looking forward for your help

All the best!

Michal