less pension credited during june 2011

Location/place: Ashwat Nagar bangalore

Name of company/service: Ex serviceman

I am drawing Military retirement pension from your bank since May 1996, every month my eligibility of pension after enhancement of DA 51% of Jan 2011 is Rs.9949/- but you are crediting Rs 8604/- How please give full recovery details. With prior intimation you are deducting why?