Then mention it again. In writing.
Build a paper trail.
Listen to your Auntie jes.
You need paper (as in, letters and return receipt requested and the whole nine yards). It's a damned site better than he said, she said when it comes to court. Paper is unbiased (mostly). It will make your case for you.
Treat this like a business. Leave the emotions out of it. He's a dick, you're hurt, I'm sorry but that's the state of affairs and it's not going to change too much but what you can change is how you deal with it.
Get mad. And get businesslike. Stop being sweet and nice about it. Courteous, sure. Nothing in front of the kids, absolutely. But you're entitled to your emotions and your children are entitled to support from their father. Even for glasses and braces and the like.
Line up the ducks. They don't line up themselves.