Change webinar participants on a monthly basis

I have requested for a downgrade in my webinar participants in February 2024, I have however received no feedback and now I need to pay for the additional participants again. I've upgraded to 3000 participants for 1 month only and Zoom customer service told me I can downgrade and upgrade participants monthly if I choose the monthly payment option? But now, I can't downgrade and now paying for a service which I am not using and I don't get any feedback from Zoom. Please urgently assist.