Make an option other than a phone number for account and secure server verification

Some people flat out don't have cell phones and making a verification system that requires them with no other options is bad design. 

VOIP and prepaid phones also can't be used for mobile verification which is another problem that could be solved with an option for a different form of verification. I've also seen some people complain about not being able to verify accounts due to their number already being used for whatever reason. This could also be solved with a different form of verification.

Email verification comes to mind or maybe some kind of captcha if you believe the account is a spam bot.