>they are faster to type from a feature phone. My customers are entering the verification phones through a computer keyboard, they are only receiving the SMS v

>they are faster to type from a feature phone. My customers are entering the verification phones through a computer keyboard, they are only receiving the SMS verification messages to their mobile phone once so I can verify that they own a phone. Unless you were assuming that their "browser" they would be entering the verification code into is on their feature phone?