Gropus Staff, adding a sales rep under the vendor

Ok I read the answer and yes I was very aware that is what needs to be done. But my question is under staff I want to add a what is a sales representative for the vendor store. Then that sales representative can be responsible for his clients that come to the vendor store and purchase products. So when the store manager or store owner looks under the sales reps and can see the list of sales reps and also see what customers they each have. I am assuming then that maybe that cannot be done under the groups and staff category.