There is levied an annual inspection fee and service charge upon each and every person, firm and corporation operating a telephone exchange in the city, in the sum of two percent (2%) of the gross revenues for each current year for exchange telephone transmission service rendered wholly within the city limits, to compensate the city for the expenses incurred and services rendered incident to the exercise of its police power, supervision, police regulation and police control of the construction of lines and equipment of the telephone company in the city. The fee shall be due and payable to the city on or before May 1 of each year, and shall be paid into and appropriated and expended from the general revenue fund of the city. (2000 Code § 7-502)