Can you still use phone data on jailbroken iphone?

I want to jailbreak my iphone 4 but i don't know if i will still be able to use mi 2gb data plan with page plus

You still have the full functionality of the phone and its plan regardless if you jailbreak it or not. So go ahead and have some fun. You still have your data

Yes you would. Jailbreaking does not change that at all.