Upgraded subscription not charging?

Currently, all members are being assigned admin gateway through a custom form. I wanted to check out upgrade process so I manually changed a test member to paypal gateway and upgrade button appeared in my account. However, when clicked it just automatically upgraded even though it should be a $2 membership fee. I am using the Paypal single payment gateway, I figured it would take me to Paypal but it doesnt. Is this because they werent assigned that gateway when they signed up, and therefore no info is on file for them?