I think you can. But it comes with a price. of course.
Anyway, you mentioned that you have an exisitng plan? Why not call 211 or 2199 and check if you can avail it with your exisitng plan.
Hi rommelgg, to make it simple just get one at any store. Phones at Globe Store are tied with plan and some were sold as prepaid but a little bit pricey compare to other retail store.