Part of the embedded form is not visible on mobile devices

We have a form here:

http://www.animalsanctuary.org.uk/events/woodlandsball

Depending on the amount of tickets you select depends on different fields appearing.

It seems to be OK with enough space on a desktop, however if you are trying this using a mobile device, if you select a higher amount of tickets it seems to disappear off the screen...

Why is the window not changing when there are more fields visible?

Thanks.

Thank you for contacting us. 

Your iFrame embedded form has a static height, and it seems to be not working properly on the mobile devices since they need more height to display the whole form. 

What you can try is to re-embed your form with a fresh iFrame code. The updated iFrame code will have a dynamic height (re-sizing the form automatically).

If you need any further assistance on this, please let us know.