Nothing contained in this chapter shall be deemed to prohibit an insurer and its insured from contracting to use a rate on a specific risk or risks which is in excess of or lower than that otherwise applicable, provided that the contract and rate deviation by consenting parties have been filed with the Commissioner prior to the use of the rate in accordance with the procedures, conditions, and limitations as may be established by the Commissioner; and provided, further, that, if the resulting premium exceeds $1,000.00, a binder of coverage may be issued and the contract and rate deviation shall be filed within 20 days after the issuance of the binder. Such contract and rate deviation shall be subject to challenge by the Commissioner for a period of ten days after filing. If such challenge is upheld, the insurer shall be required to use its regular filed rates for the first 30 days of coverage in accordance with the requirements of applicable law. If there is no challenge or if a challenge is not upheld, the contract and rate deviation agreed upon may be used from and after the effective date of the binder.