As u told ,i checked the the PRIFILE in BSC and found that:-
00760 AMR_HR_IN_USE_IN_BSC NOT IN USE
00283 HR_FEATURE_IN_BSC ACTIVATED
However other BSC having same setting although call is going on half rate in those BSC.
want to figure out one more thing as i think this should be from site end as there are few cell in that problematic BSC where call is going on half rate.
need ur suggestion.