HDFC Bank — fraudulently changed AMB policy

Address:

North Delhi, Delhi

When i opened my A/c few years back I had to maintain Rs5000 as minimun average A/c balance and that was calculated quarterly , but recently i noticed they have been charging me AMB( average monthly balance) cess every month since jan 2012 so i visited my branch and asked for the clarification then i learned that bank has changed its policy now i have to have minimum Rs10000 and that to every month . But i never got any intimation for this change never they have mail or call me to inform which they always do for every other silly reason . They have almost charged me around Rs4000 . Please help i want my refund otherwise i am going to close my a/c