It was worst when my own kids were little and they just copied them. I sort of felt better letting teh daycare kids call me mom than asking my own kids to call me by my name during daycare hours. The older they get the less they do it. As long as they are using your name some of the time then the issue is starting to go away.

As some have said kids just assume that all women are moms and all men are dads just as they go thorugh association phases where all 4 legged small animals are dogs and big ones are cows or whichever two they pick.

When they call you mom you can just say my name is "-------" what would you like. It will come. Evetually start not answering to mom by looking at them when they say mom and say no I am.... but not till child is at least 3-4. Their curiosity about the world they want to share with you is more important than how they get your attention. Don't squash their enthusiasm yet.