If I get an IPhone do I have to change my plan?

Ok, so right now i'm with Virgin Mobile. I decided that I want to upgrade to an iphone this summer, but if I have to change my plan I don't want it anymore. And right now I have the 45$ plan, if that means anything. So… Do I have to change my plan or can I just buy an iphone from virgin mobile and just stay with the same plan?

I fail to understand why you're asking your question here instead of asking Virgin Mobile.

If you want to stay with virgin, either buy a pay and go iPhone from them, or make sure its unlocked if you buy it from anywhere else, this lets you use any sim card such as orange, O2 etc. It will also work for virgin, then you need to make sure that the sim card will fit into the iphone, different models change in terms of sim card size from standard to nano, check when you get the iphone, and you can try cutting it down to fit, thats what i did and i changed from a HTC to my iphone 4s fine with the same contract