Two Factor Authentication no backup SMS

I have set up Two Factor Authentication on my account and have configured it to use the Google Authentication option and this works fine. But in the event I loose access to this authenticator i tried using the "Can't access your smart phone" option and chose the option to recieve an SMS via my Alternative Numbers, but an SMS is never sent. I then tried the Get by phone call and that did work. Is there some way I can get the SMS option working as a backup?