ISTA North America Improper and Unfair Billing Alpharetta, Georgia

I live in an apartment complex served by ISTA.  Each building has 16 units, however, there are no individual meters for heat or hot water.  As a result, ISTA uses a formula composed of square footage of each individual apartment, as well as the number of people living in each unit, to come up with your monthly heating bill.  The problem is, ISTA makes no allowance for vacant apartments.  As a result, each tenant subsidizes the landlord for heat usage in occupied apartments (there is no way to turn off the heat in vacant apartments).  At any given time, there are 3 to 4 vacant apartments in each building.  Therefore tenants are paying the landlord's expenses to heat these unnoccupied units.  Seems like a ripoff to me.