One errant click on the settings page and you lose your number. A notice to that effect and a confirmation request seems like a good idea before going ahead and removing the phone from the account. On the plus side, turning it back on (with a new number) is easy. I'm not sure this is good for Ting, though, if it costs Ting $35 each time. Someone may try playing the number lottery until they get a result they're satisfied with.
"Remove device from account" Confirmation