I’ve called him several times and no answer

We broke up months ago but now this clown won’t even answer the phone when I call about the kids. I’m pissed. He didn’t call them for Christmas or New Years. Our son first birthday is coming up and I’m sure he won’t bother calling for that or sending money to help with daycare. I really just want to block him now because I’m so mad. How can you go months without talking to your kids? What’s wrong with some men? Ugggh