Do you need to keep the Tmo number active to keep the GV number? I was doing the same as you, but as I decided to retire, I won't be travelling for work so I decided to let the Tmo plan slide. To that end, as an experiment, I unlinked the Tmo number from GV and it has been working fine for a couple of months now. Now, there may be other reasons for you to keep the Tmo number, but it doesn't seem to me that I need to keep Tmo active any longer.