I have a nokia 6500, which i got on a plan, with my internet provider?

[mellyj1982231]

I am wondering if anyone knows if i can upgrade to a new mobile while i am on a contract, its for 24 months, which i have got until march 16th next year, I seem to be having trouble with this current phone , I am able to charge to via the computer but when i do, when i take it off, it seems to chew up the battery more and every so often it turns itself off or freezes when i am on the internet, I am with Iprimus which is an Australian Company, which means I am in melbourne Australia.
it is a nokia 6500c.... not a slide up one