The AirPods Pro service program described in AirPods Pro Service Program for Sound Issues - Apple Support is specific for AirPods manufactured before October 2020. It sounds like your local Apple Service has checked and your AirPods are not part of the defective manufacture, so your entitlement would then be Apple's 12 month warranty, plus any AppleCare cover you purchased. They have found your AirPods are out of warranty which means any repairs or replacements are chargeable. Your best option might be to buy a single (left) AirPod as a replacement part. This is usually arranged through Apple Support, but if service in Botswana is through a third party service company it might be a little more complicated.
I don't have details of the Apple Service and support function for Botswana (about 6000 miles away!) but Apple's support site AirPods Repair & Service - Apple Support should guide you to the replacement options. Hopefully the site will pick up your location and take you to the options for Botswana. If it comes up in US $ you might need to search again after selecting an appropriate region or country.