Well, there are quite a few ways of doing it.
If any of them work?
Personally tried and didnt.
Went all the way to prestige 7.
Left PS3 On all night,was prestige 7 level 20 before the contracts updated at 12.00.
In morning,Switched PS3 Off,then back on and i was back to Level 1 0 Prestige.
I cant be arsed to try again.