does it cost anything to upgrade my plan in say 5 months for example from what it is now to a better one?
When you change your plan to a different one (more expensive) you see a credit for the old plan from when you changed it and you see new charges for the new plan plus a month in advance. Current plans are alright for the most part, in 5 months it may be completely different. If you wanted to change your plan, I'd suggest changing it at the beginning of your billing cycle so you do not incur any extra charges on the next bill. Hope that helps answer your question :)