ill treatment

So I am at spar in Berea, East London, on Monday to buy lunch cause they really cook some progressive veggies there, anyway we are standing in a queue being served by two black ladies who were struggling to cope with the long(ish) queue. Then there comes this white lady from the other end of the food counter to come help out, only she walks past us and starts serving the white gentleman behind me and of course I didn't take kindly to this but after noticing that it's an old white gentleman I calm myself down (despite the fact that she could have at least politely asked to serve the old man first to which I think everyone would have gladly nodded ). It was when she started serving the second white gentleman behind me that I called out \excuse me Mam