790? Is that on all 3 agencies? Either way, that's impressive!
IMO, they should have let you bill it based on your score alone, I would have, but from what I gather, it isn't just the credit rating they look at alone, they also look for a long history paying long-term substantial bills with the same company (although I am sure with your score you qualify in that area too, unless you change providers of those billable services alot).
I read that D* lost alot of revenue due to people not paying on time or at all, this may be a defense mechanism put in place (i.e. they don't trust us, keeping in mind that it is well known that some of the richest people are the worst at paying back loans, doctors and lawyers have the most deliquent student loans out of all other student types and financial classes).