Within thirty days after receiving a properly submitted bill for medical payments, the employer shall:
(1) Pay the charge or any portion of the bill that is not denied;
(2) Deny all or a portion of the bill on the basis that the injury is not compensable, or the service or charge is excessive or not medically necessary; or
(3) Request additional information to determine whether the charge or service is excessive or not medically necessary or whether the injury is compensable.