ISTA HOT WATER RIPOFF DALLAS, Texas

i live in a multi-unit apartment building. the people who oversee the property hired a company called ISTA to collect  the utility bills. (heat  and hot water).  well they do have meters to monitor the heat but not the hot water.  so ISTA uses a system they call" RUBS".  they say its the only fair way to do it since there are no meters.  some apt. have 1 person living there, others have 5  or 4 people. ista has no idea of who lives in the apts.  SALLS who manages the apt. building, might rent an apt. to 2 people and 2 or 3 might move in with them later.   point is i am paying for hot water all the other people use. and thats what ISTA  told me. the more hot water the building uses, the higher my bill would be.  another thing is, the renters have no idea what the bill is for the building, so they can charge whatever they want. i am sure there is a law that would prohibit them from using this method. put meters in!!!  i don't mind paying for hot water that i use.