As phones become the central feature of our lives, they also become targets.
Recently, a number of high profile people in the world of Bitcoin have had their phone numbers stolen right out from under them.
Thieves call AT&T or whomever and pretend to be the owner of the phone number, but have forgotten their security codes, etc.
Through clever manipulation, they manage to get the information, port the phone number and then, with that, use the SMS codes to log in to people's accounts...and steal their Bitcoin.
You can read about the full story here in Forbes.
The fix may be intense but it's worth exploring how you can lock things down. Kraken wrote it and it's pretty deep. Not sure you need to do all of it.
The point is...the phone is your central point of action/security and if you lose the number, you become vulnerable.
You may not own Bitcoin, but your phone number is pretty central to almost everything.
And, for the love of God, please use a 2 factor authentication code instead of SMS whenever possible. I prefer Authy.
It may seem like a lot of effort, but an ounce of prevention...