AT&T has begun offering refurbished iPhone 3G units through its online store. The company is charging $150 for the 8GB model, while both the black and white 16GB models sell for $250. As with normal, non-refurbished units, these refurbs require a two-year contract. The move follows last week’s quiet launch of online sales for new iPhone 3G units from AT&T’s website. Apple has yet to offer the iPhone 3G, either new or refurbished, through its online store in the U.S.