There is a nefarious practice of stealing people's phone numbers to intercept their phone calls and text messages, and it is fairly easy to do if you know what you are doing. The attack involves calling the wireless carrier and convincing them to switch your phone number to a new device.
This type of social engineering attack is hard to combat, and a difficult problem that all mobile carriers are dealing with. In fact, this problem is so pervasive, that many institutions and companies are starting to turn off SMS (text messages) as a way for Multi-Factor Authentication for their services (IAS does this as well).
Android Police recently came out with an article on how to protect yourself from this type of attack by setting a transfer pin on your mobile phone number. This means if you legitimately transfer your phone to another carrier or device, you'll need to unlock the transfer with the pin before it can happen. This is similar to a credit freeze that you can put on your credit to ensure no one is taking out credit cards in your name.
For more information on how you can protect yourself from SIM Jacking, take a look at this article.