Hi @Atommo75,
Thanks for your post, and a warm welcome to our Community Forums.
I'm sorry to hear there are some problems with the SIM size for your Son's phone. I've had a look on our side and it does seem that the SIM you have, is the SIM type advised by @enlli.

It should look something similar to this. And you would have the ability to push the chip section out. Are you able to take a photo of the SIM you have? When fitting the SIM, please ensure it's the correct side, and you should see a small angled line on both the SIM, and the SIM Tray - similar to this image here.

Cheers,