Tolls shall be received for passing a bridge only after it appears to the circuit court of the county where the bridge is located that the bridge is completed according to the act authorizing it. The court shall ascertain whether it is so completed by appointing three disinterested freeholders to view it. If they report in writing that it is so completed and their report is confirmed by the court, the person authorized to erect it, or his heirs or assigns, may then demand and receive tolls at the rates fixed by such act from persons or things passing over the bridge. If no rates are fixed, then he, or his heirs or assigns, may receive tolls at such rates as may be fixed by law. If the toll rates are specified in such act they may be changed by law, unless such act otherwise expressly provides.