Can I use My Contract Phone's Sim Card And put it into an Iphone>?

I have A Samsung Galaxy Ace and I want to upgrade to an Iphone but my contract ends mid next year and its too much to cancel the contract. Can I use The Sim Card I have now in an iphone? By the way I'm on a new network called TalkMoblie

You will need to change the sim to the correct size to fit the iPhone. This will be a micro sim, or a nano sim, depending on which iPhone you choose to buy. If the iPhone is a 3g, or a 3gs, then the sim is already the correct size. If it is an iPhone 4 or later model, it will need to be changed to the correct size, otherwise it will be too big, and won't fit. The iPhone will need to be unlocked/sim free or locked to Talkmobile. Talkmobile uses the Vodafone network, so an iPhone locked to Vpdafone may work too, but I can't guarantee that. You will have to pay full price for the iPhone, if you don't have one already, but as long as you follow the above advice, you should be able to swap the sim with no problems.