S.M.
We handle this a couple of ways. 1. Don't leave a message. If the child she wants to play with isn't home when she calls and you know you are going to call someone else, don't leave a message (if its an answering machine). If someone is home simply say "I was hoping Sarah could come play, but since she's not home, I guess we'll do it another day". 2. Have the friend you called 1st come over along with the other child if this is practical. 3. If you don't want the 2nd child coming since someone is already there, I would answer for the child saying "oh Sarah, thanks for calling back, Megan wanted to see if you could play today, but unfortunately, she isn't able to play anymore. We'll call you another day." Or, if you didn't call the friend and they are just calling to play, simply say "Megan already has a friend over, can we try to do it another time?" You can also invite the child over, again, if you are OK with that, or just set another day for a playdate with that child.. I don't see any reason to lie or anything like that. But to stop the situation from happening, just don't leave a message.