IPhone :: Way I Can Get My Number Ported

I'm a new AT&T customer, coming over from Verizon and would really like to keep my existing phone number. I called AT&T's porting department last night and was told they cannot port my number over because my number is from an area where AT&T does not have service (my number is originally from Southwest Minnesota, where I used to live -- AT&T is pretty much non-existant in the area). I'm told they need an address, in that area, that has AT&T service.