State Bank Of India [SBI] — maintenance of minimum balance

Address: 500013

Sir, i have a saving bank account in your bank. I have it for last 12 years. I have a meagre income of 3000 p. M. Last month about 500 rs was deducted for not main taining minimum balance. This is what i spent for my child s milk. It is arbitrary to ask me maintain a minimum balance. Which i cannot afford. Kindly return my money this amount deducted from a poor mothers account was meant to feed her only child. Please help me