broken pipe

water authority was trying to fix a leak in front of my house,almost on my property very close.they broke a pipe somewhere under my foundation.and then told me to get a plummer and also billed me for $716.00.they said it is my problem because the pipe is on my property.i no this but they are the ones that broke it.pipes like that don't just break for no reason.they are made strong.unless there is digging and pulling and chopping and banging near the pipe.which is what happened.this water is still pumping under my foundation as i try to reach out here for help.i am 61yrs. old and live by myself and don't no what to do.please someone help me.