Accidentally remove Apple Care, How do I reinstate it?

I had 2 iPads for my grandkids, and I had Apple care for them , one day I was checking something they claim on apple support that I requested to cancel the apple care on one of them. I emailed them talked to them ( five or six people) and they no we can’t reinstate it. I’m so furious. Please advice me how to go about reinstating this.

[Re-Titled By Moderator]