No sickness and accident insurer shall make or permit any unfair discrimination between individuals of substantially the same hazard in the amount of premium rates charged for any policy or contract of such insurance or in the benefits payable thereunder. This section shall not prohibit different premium rates, different benefits, or different underwriting procedure for individuals insured under group, family expense, franchise, or blanket plans of insurance. This section shall not limit the negotiation of preferred provider policies and contracts under sections 44-4101 to 44-4113.