Mahanagar Telephone Nigam [MTNL] — Continuous balance deduction from my account

Address:	New Delhi, Delhi, 110059
Website:	mtnldelhi.in/dolphinnew/pg.htm

I had recharged my mobile of Rs100, After using few days balance left was around 60+rs but other day balance was 20 and now it is 4. I had called customer case but they are saying please call later as there system is not updated yet. I tried that too but no help. So please help me getting my balance back.