sizing window on a website

Hello
I have a dell computer with a new 21.5 inch flat screen monitor. I have a question. I go to my cell phone carriers website frequently to conduct account business. While there, if I want to make a change to my account, there is a window that pops up(inside my web browser window), that asks me to review my account changes and charges and then click on the "submit" button(at the bottom of this pop-up window) to agree to these changes and charges to my account.
I went to my cell carriers website today, and wanted to make a change to my account. I selected the option that I wanted to change on my account and clicked "continue" at the bottom of the screen. Then, about 30 seconds later, the pop-up window appears(described above) and asks me to confim and agree to the change/charge to my account. The problem I am having with the pop-up window that appears, is that I can't scroll down far enough to see or click on the "submit" button to make this change to my cell phone account. My question is: how do I adjust or resize the pop-up window on my cell carriers website, so that I can see and click on the "submit" button" to make changes to my account? I have tried a couple things today:

[*]Expanding my browser window - Did not help
[*]Hitting the return key - Did not help
[*]Expanding the bottom of my browser window - Did not help
[*]Tried moving the pop-up window - Did not help

What am I doing wrong? Some help with this would be most appreciated Is it even possible to re-size a pop-up window on a website to work with it, when you have a 21.5" monitor like I have. Just wondering?? Have a safe Independence Day.

Thanks