Can you cancel your plan with Virgin mobile at anytime?

I'm a 17 year old student, and I can afford to get my own iphone. I want to get a pre-paid plan through Virgin for 30$/month. I was wondering if this means at anytime I can just cancel it, no commitments, nothing? This sounds too good to be true…
Also, can I buy one without my parents co-signing, without having established credit?
http://arstechnica.com/apple/2012/06/at-30month-virgin-mobile-beats-crickets-prepaid-iphone-plans/

Www.google.com/voice

just sign up with your gmail account 100% FREE.

Phone number is "free"
all usa and canada calls are free "unlimited mints"

+ with a obi202 off amazon.com you can hook that up to your computer
hook up a phone to the obi202 and use it to call

or you can call on the computer with a headset

for $0.00 each month you'll get
phone number
voice mail
unlimited minutes

and lots of extra cash from never seeing a phone bill again.

I use it, mom loves it no bill

in google voice you just click off your old phone and click on "google chat"
and it forwards the number to its self and lets you call.

sound quality is excellent
Love google's phone service.

to call from gmail you just hook up a headset and their is a phone icon on the left
then a dial pad shows up on the right

the voice mail appears to be unlimited storage?
and message don't get deleted like with a cell phone after 14 days none of that.

Much better service at a much better price free.

Lots of extra cash with no bill ever again.

phone number is free to!
and you can check it when ever your at a computer.
play the message in the email etc.

you'll get voice message and it transcribes it into text so you can read it to
download the message as a mp3 and even copy and paste it

+ with google voice dialer addon for chrome you can click on numbers
and it will call google "talk" and your phone hooked up to your obi202 will ring
you answer and it calls the number you clicked on makes calling someone very fast and easy.

Best wishes,
Mr.