You might have luck writing them and asking -- I assume you didn't make Summit on segments (30), yes?
I really wish that Frontier would give customers the option to purchase elite-qualifying miles or segments. It just seems like such a no-brainer to me. People do mileage runs / segment runs to maintain elite status. Why not allow something simlar without having people actually fly? Take my money and give me my elite miles or segment, but don't make me waste the time to actually fly and sell that seat to someone else.
It may make sense to put some cap on it so it is impossible (or at least really expensive) for someone who rarely flies Frontier to buy elite status. But for someone who is a fairly close to hitting an elite tier, paying to bridge the shortfall would be a nice option. Certainly not everyone's cup of tea, but some would jump at the idea.
It's not only beneficial for the customer to be elite, but Frontier benefits from having customers invested in their FF program too. FF program addicts do things like seeking out the carrier and doing milage runs. If someone wants to pay you for the privledge of becoming addicted to your FF program, why not let them?