Pleassse help! Kids father won’t let me speak to the kids while with him. I have kids 95% if the time

I have custody of the kids.

We were never married. He left when I was 6 months pregnant with our first. (Like disappeared and moved to FL)

Our daughter was 18 months old when he met her. He wanted to come back. I gave him a month to get a job. He refused to get one. In that time I was pregnant with our second.

Regardless I kicked him out because he hadn’t changed.

And please don’t guilt me for getting pregnant again. It wasnt planned. I was breast feeding and never had a period. I told him to pull out and suddenly “he forgot how” so he says. Still, I know I’m at fault. Love my son though so dont shame

Anyway, he went back to FL and then ended in Missouri with his folks.

In our court agreement we agreed to Skype three times a week.

He only calls randomly. Sometimes he goes months with out calling.

We also agreed he would visit the kids in MD every three months before taking them to MI.

Thirdly I agreed to less child support, (600.00 a month for both kids, so 600 totally a month) if he visited.

So had more money to save for travel experiences.

Well he hardly calls and never visited. Maybe once a year for two day.

And also stopped paying child support.

For the kids I wanted them to have some relationship so I would agree to either one or two weeks in MI per summer.

Well, the last two times he refuses to let me speak to them.

I ask him and he responded “were busy” and so in.

It’s not even about me.

I’m worried that the kids get home sick. Just a hello on the phone for one minute is fine! Just something to give them peace.

Am I wrong?

If not wrong what can I do??? Anything?

I work in the courts. I studied developmental stages of children and teach a co parenting class.

I know what’s good for them but what do I do when I parents won’t co parent??????