My bank started using 2-factor authentication with phone being part 2, so I am wondering is it difficult for someone to impersonate my mobile phone to receive the text message with the code?
NIST (National Institute of Standard and Technology) is recommending not to use SMS based 2 factor authentication. According to NIST guidance.
OOB [out-of-band verification] using SMS is deprecated, and will no longer be allowed in future releases of this guidance.
This article by Brian Krebs has details on how the current 2 factor auth using SMS can be used by bad guys to scam people. It also has details on the alternatives which are more secure.
SMS is easy to intercept because of the SS7 protocol used by carriers which was designed with no security.