What about having a quiet activity ready for them? I kept a box of toys or books near my desk for calls. It helped keep them busy so they didn't interrupt.
Totally get this now after trying it myself. I used to hand my kid the same puzzle during every call until he got bored and whined. Then I saw what @baker.willow said about rotating the stuff in the box, so I swapped the puzzle for some stickers and a coloring book. The new quiet activity kept him focused way longer so I could actually finish my meeting.