SMS Marketing is Ridiclously Difficult and "in Beta" at best, you should refund everyone!
1) Customers who sign up for SMS should not have to sign up again after they sign up by responding "yes" to a text. They already signed up! You can offer an opt out but signing up twice is unnecessarily difficult and not consumer friendly!
2) Until you fix number one and stop harassing your customers with your "CYA" nonsense, you need to add a feature to the contacts that have not responded to your unnecessary double confirmation system that allows the contact to recieve a reminder text.