Benefits are overdue if not paid within 30 days after the insurer receives reasonable proof of the amount of the benefits. If reasonable proof is not supplied as to all benefits, the portion supported by reasonable proof is overdue if not paid within 30 days after the proof is received by the insurer. Overdue benefits shall bear interest at the rate of 12% per annum from the date the benefits become due. In the event the insurer is found to have acted in an unreasonable manner in refusing to pay the benefits when due, the insurer shall pay, in addition to the benefits owed and the interest thereon, a reasonable attorney fee based upon actual time expended.