Hmmm....a lot of different answers here. My dad was the tenth customer for Qwest Wireless and I can't quite remember if he could choose his number, but they did have an option to choose the same number as your home phone, so it'd ring in both places. We did however, get a number that was similar to our phone.
I think the people at the stores can somewhat choose. When my mom went to Sprint for two new lines, the clerk was able to give her similar numbers (303-257-XXXX).
When I went to Verizon to get my phone, while they were processing it, they said "Is (###-###-####) okay?".
I don't care about the prefix, just the last four digits and the area code. I think certain carriers have certain prefixes. My friend and I are on Verizon and our phone numbers are (303-489-XXXX). 303-437-XXXX seems to awlays be Sprint here. I don't think it'd be too hard to get my last four digist of my choice it T-Mobile has their prefixes.