I would like to gently suggest that focusing on face blindness, while fascinating, is a derail from the OP's actual issue and a denial/distraction from the racism apparent in the treatment she is facing.
Yes people have varying degrees of recognition and memory issues, but when you are a person of colour in a majority white environment, having your identity and individuality carelessly and repeatedly diminished, and people laughing about it, as the OP described is very problematic.
Also the knowledge that in correcting people you make yourself an active target rather than just a passive one. It also takes strength and confidence to pipe up and say: that is not my name. It even takes mental energy to ignore until the other person self corrects.
@GreenEggsAndShame if you feel strong can you correct (with a smile if you can manage it) just to say : my name is...
If you feel really bold you could try asking why do you keep calling me that, it's mot my name
If you feel funny you can answer with "yes Barry (not name of person"
If you feel bolshy you can ignore.
But all of it is crap and you shouldn't have to. And you always, as we have seen played out on this thread, risk a defensive/aggressive response of denial and accusation.