I just got a iphone 4g and i wanna facetime but does it waste my internet?

I could afford an iPhone 4 but I need a fairly cheap contract so don’t want to fork out £200 on the phone, I already have an iPod Touch 4g but I want a good phone for Facebook, texting and games and some music, not bothered about BBM, while out and without my iPod, should I go for the 3gs or a blackberry (probably a bold or curve).
Also, are Three good for coverage, would it be better going on O2 but with a worse contract?
Thanks guys, going to look around at 3GS contracts, may wait for the 5 and see if the 4′s price drops, definitely going iPhone though.

I want to buy an iPod Touch 4G but my dad is against it as he likes all microsoft things, like for example i had to wait half a year for a windows phone the HTC 7 Mozart instead of buying an android phone which i admitt im glad about because the HTC its better then an Android phone and iPhone anyday but my dad wont let me get the iPod becasue he says wen you download iTunes it will change the file format of my music on my computer already and it will basically act like a virus because we dont have any other Apple appliances, only windows.

So basically if anyone has Zune on their Comupter, i want to know is it anything like that? and iTunes is a seperate application on your computer so it wont mess things up would it?
I just need information on iTunes and what it is like to help persuade my dad, Thanks !
But what File formas are compatible with the iPod? is MP3 compatible?