The water company will read your meter, and see if the leak indicator is turning. You can do this yourself for free.<quoted text>
Yep, that small amount could save you. But I'm not sure if they actually do anything when they check. So you might have to hire a plumber anyways.
Look at your meter and check the meter reading. If you see numbers higher than your last bill then your meter was not overread. Read your meter every day for a week. Write it down and see how much water you are using. Turn all water off and check your leak indicator on the meter. If the leak indicator is turning, find & fix the leak. Check the condition of your toilet flappers, make sure your float is working properly. Make sure your chain is not hanging up when you flush.
If you still can't find your problem, call a plumber.