No notice of cancellation of a policy to which Section 27-23-21 applies shall be effective unless mailed or delivered by the insurer to the named insured at least 20 days prior to the effective date of cancellation; provided, however, that where cancellation is for nonpayment of premium, at least 10 days’ notice of cancellation accompanied by the reason therefor shall be given. Unless the reason, or reasons, accompany or are included in the notice of cancellation, the notice of cancellation shall state, or be accompanied by a statement, that upon written request of the named insured, mailed or delivered to the insurer not less than 15 days prior to the effective date of cancellation, the insurer will specify the reason, or reasons, for such cancellation.