RCS

According to Apple's list:

Wireless carrier support and features for iPhone in Africa - Apple Support

no African cell carrier supports RCS at this time. But you can check if your carrier supports RCS by opening Settings, selecting General, and then About. Scroll down to the “eSIM/Network” section. You’ll see a line for “Carrier.” Tap on it to switch that line to “IMS Status.” If your carrier supports RCS, the option will show Voice, SMS & RCS. If not, it will only show Voice & SMS.

Regards.

RCS requires that carriers support it. Even in the US and Canada, not all carriers are up to speed. Apple cannot force carriers to enable new services.

Not all carriers support RCS on your iPhone, so that should be your first contact. In addition, all Android phones don't support RCS, so using it to message a particular phone may not work either.