Until December 31, 1997, a tax is imposed upon the act or privilege of originating in this State or receiving in this State interstate telecommunications by a person in this State at the rate of 5% of the gross charge for such telecommunications purchased at retail from a retailer by such person. Beginning January 1, 1998, a tax is imposed upon the act or privilege of originating in this State or receiving in this State interstate telecommunications by a person in this State at the rate of 7% of the gross charge for such telecommunications purchased at retail from a retailer by such person. To prevent actual multi-state taxation of the act or privilege that is subject to taxation under this paragraph, any taxpayer, upon proof that that taxpayer has paid a tax in another state on such event, shall be allowed a credit against the tax imposed in this Section 4 to the extent of the amount of such tax properly due and paid in such other state. However, such tax is not imposed on the act or privilege to the extent such act or privilege may not, under the Constitution and statutes of the United States, be made the subject of taxation by the State. Beginning on January 1, 2001, prepaid telephone calling arrangements shall not be considered telecommunications subject to the tax imposed under this Act.