What is wrong with the game? (Call of Duty MW 2....Xbox 360 and Online rank)?

I've been playing online and leveling up. I have reached level 70 and the next level (71) is Prestige. When I go to the barracks to check my progress it says that I need 0 Exp to get to the next level. No matter how many times I play and win and restart the system I never get up to level 71 (Prestige). I usually gain a few thousand points of Exp but haven't leveled up even though it says 0 Exp required for next level. What is wrong?What is wrong with the game? (Call of Duty MW 2....Xbox 360 and Online rank)?
u have to go to the barrack and press enter prestige mode. U dont prestige automaticly