What is the ruling of Islamic law regarding a driver's refusal to accept the agreed-upon fare, and his demand for a higher amount on the pretext that he misheard the agreed-upon fare?

The consideration for the amount of the wage is what was agreed upon in the contract, and there is no consideration for the intention of the employee to demand more than what was agreed upon. However, if they differ on the amount of the wage after the benefit has been consumed, and neither has proof, many scholars have held that both parties must take an oath. If they both take an oath, the employee is entitled to the wage of similar services. If one of them refuses to take the oath, judgment is given in favor of the other party. Some have held that the statement of the hirer is accepted with his oath. If they differ before the benefits are consumed, they both take an oath and the contract is rescinded. If they differ after some of the benefit has been consumed, the statement of the hirer is accepted with his oath regarding what has passed, and they both take an oath and the lease is terminated for the remainder.