This happened with our water bill over the time we were getting married. We had 5 people staying with us for our wedding (7 inc us) and we were expecting a huge water bill, with 49 showers in a week and not counting all the times the loo was flushed. Anyway the bill came in and our actual cost of water usage only read $4!!
I rang them and they came out to check and the water meter had packed in, and probably happened not long after our meter was last checked. They never gave us an estimate cause it was no fault of ours, and so we only had to pay the usual other fees and our $4 of water :).