I expect my coworkers to know my name.
Do they not know your name? It's reasonable to expect your coworkers to know your name.
I've told them my name, but they always seem to forget it.
There are many people who have problems remembering the names of others. There are so many people out there, so if someone messes up your name every now and then don't take it as a sign of disrespect. Everyone makes mistakes.
If you say so.
I think it's always best to give people the benefit of the doubt. Everyone forgets things from time to time, and I'm sure it's not personal. If it continues to happen though, you can calmly try to explain to them how you feel.