Water meter out of control. Utility not helping - Please help!!!

[Mike A.]

We've owned a building for about 3 years in the city. We just received our water bill for said building last week. We called the useless water dept, and they sent someone out. The water meter is going out of control, but we couldn't find the leak. We sent two different plumbers, they couldn't find a leak either. The water dept has no idea what's going on and offers no assistance. Meanwhile, for a six unit building, we have a 2.5k water bill that is normally around 500.

Anyone ever have a situation like this? What do I do? Please help.