How to deal or not deal with a smear campaign

We've been broken up for a year and no contact since May. We did work together but he decided to leave a month ago because he was "offered" a different position and it was below him. Now he's unemployed because he isn't as great as he thought. 2 different customers have come to me and told me he's saying he was let go because he broke up with me. Totally NOT true. Not saying I didn't do a happy dance the day he quit.