Stop my kid from deleting vpn off their phone.

Hi Mats2583,

Welcome to Apple Support Communities. You can restrict your child deleting apps from their device using the parental controls on your iOS device. Go to Settings > Screen Time > Content & Privacy Restrictions > iTunes & App Store Purchases, and set "Deleting Apps" to Don't Allow. More info on this is found in the related article:

Use parental controls on your child's iPhone, iPad, and iPod touch - Apple Support

Let us know if you have any questions.

Cheers!