Iphone data usage? How does it work?

I have Wi-Fi at home and all I'm pretty muchly going to use to Wi-Fi for is listening to pandora on the way to work and on the way home from work. It's a 15 minute drive there and 15 minutes back so 30 minutes a day 5 times a week so 150 minutes of data a week and 600 minutes a month at minimum, depending if I don't you GPS or anything like that. Do you recommend 300 mb or 3G data plan? If so why and does data plan go off the amount of time you are on the internet or the content that you download, because in that case I don't plan on downloading anything just listening to music and getting directions.

Its all depends on your choice. If you wish you can use data plan or you may also use internet. Just think about your choice clearly and take decision and that must be correct. Best of luck.