Replying to Upgrading my POS phone

So at LEAST three years ago I upgraded phones from a motorola razr (remember those?) to some shitty pantec phone. Swam with it two months later and killed it, so i've been using a blackberry bold and older blackberry 3xxx or whatever. My bold is shitting out, so it's time for an upgrade!

Now I have some questions:

Can I buy a refurb iphone 4 (not 4s, not 3gs or 3 series, a 4) online and use it WITHOUT a data plan by switching sim cards? I've heard yes, but want to double check. Its possible to shut off data via 3/4g in phone, right?

Is it better to go that route and save on data? I don't use internet when im out and about so it wouldnt be a problem.

I know you have to get some form of data plan when buying a smartphone through AT&T (my carrier), is there any way to avoid this?

I qualify for an upgrade anyways, do i save on buying an iphone online and man up and get a data plan?

Thanks for the help guys and gals!