Two-factor authentication methods like SMS verification are not possible without internet connectivity. An
SMS verification code will be sent to your mobile, regardless of whether or not you're online. Even in
cases where offline authentication is unsuccessful (e.g. camping) users will be able to immediately
identify the issue and take the necessary steps to prevent it happening and again, before waiting for the
time when they are connected again. In case where you require a full article about phone verification
service, look at this website.