No achievement for halo 3 70 exp?

[Ferhan]

Hi guys, i just got up to 70exp for halo 3 online for liunenent or how ever u spell it and didn't get both of the achievements for spartan officer, i have 10 highest skill and 70 exp but no achievement???

 

[Tony Von Awsomo]

call bungie

 

[Kevin R]

You need to get it in one playlist i think its 50 xp in one ranked xp playlist