If, during the term of the franchise, there shall be enacted by the Iowa General Assembly a valid taxing statute authorizing the City to collect a tax on the telephone revenues received by Grantee from its customers in the City, or from any other type of communication service conducted by the Grantee within the City, and if such tax is levied by the City, the Grantee shall collect said tax and remit the sums collected to the City under the terms and provisions of such enacted statute.