Popup Close Button

Hi,

The popup has a place for a button and link. When we add the button in, the popup reopens every time you close it.
Is there a way to have the button that acts like a close button so clicking on it will just close the popup?
Popup is on this page - https://www.camfour.com/bill-pay/

Or is there a way to make the X that closes the popup an image. Or can you make an image a close function?