So if I use the 10gb and also use 2gb over for $10 more, can I pay $50 for 10gb now or do I have to way for the following month? Basically can I start n pay early or am I limited on how much I can buy every month?
That's something wrong on their end. Did you update profile and prl under system updates and turn you phone off. Sometimes their changes are anything but immediate. Anytime you run out of data on the $50 plan start a new plan because at an add_on cost $10/2G is the same as $50/10G.