Welcome. There are some companies that do shops internationally though I don't recall seeing any that were in Africa. You may want to get signed up with Bare International and Gapbuster. Most of the shops and companies mentioned in this forum do shops in the USA and Canada. There is a fairly active mystery shopping community in Europe.
The New Mystery Shopper section of this forum will help you with some ideas from a shopper perspective, but somehow I suspect you might do better going to the main offices of companies in your area and asking them if they are mystery shopped and if so, by whom. If you have become somewhat familiar with mystery shopping, you might even be able to arrange shops to do for them yourself.