Whenever I have cancelled a pre paid I have always had the refund credited to my credit card and it has always shown within a couple of days -
As for the points I had a pre paid last week at MIA - Yukon/Tahoe for 1 day and got 6 points for the sat radio cost - however also got 400 bonus points for some reason
= however due to the improved rates for pre paid you do not get points. so see what the difference is between pre pay or pay at location before deciding on the pre pay rate - sometimes the difference is small so not worth losing the points etc