Anyone familiar with water meters ? UPDATE

If you had a city inspector come and tell you the meter is running when everything is off and no leaks, the meter is defective
The city has records of your bill and that type of increase in usage with no plausible explanation is unusual
Keep calling and keep protesting the bill until the city changes out the meter, have dates when inspector came out initially and statements of "licensed" plumber stating no known leakage found
Best of luck and I know how frustrating dealing with the city/utilities can be from personal experience