Good evening Simonb1962,
Welcome to the forums & thank you for taking the time to post.
I am sorry to hear that you phone has been stolen, always a headache.
When you log in to your TVGO on the device management tab you will see this
"When you watch TV on a new device and have already used all of your devices, TV Go will ask you which one of these you want to replace."
So whilst you can't delete the individual device you can replace it one the device slots are full.
Kind regards,
Zak_M