Blackberry Curve 8330 lagging?

I just got my new phone four days ago and worked perfectly. Set up my e-mail, contacts, etc.. Well, now it has started to lag badly. When I am using the browser and want to close it, normally it would close instantly and now it takes atleast 10 seconds just to close. I watched Sprint TV on it two days ago and it was perfect, but suddenly today, sound and video on it just became laggy and the screen would freeze at times. Even just going back from the app screen to the home will lag for a few seconds. Should I return the phone or is there something that can be done? Could the apps I bought caused it to lag, also? Any help is appreciated.