In an email that Phone.com sent out to all of it's customers earlier this month:
Phone.com is instructing everyone to login to their Phone.com account and click where it says "SMS Enrollment" to fill out the registration form.As part of U.S. wireless carrier efforts to combat spam and improve the delivery of legitimate text messages, a significant industry-wide change is occurring. Customers that send text messages using local phone numbers must register with a 3rd party reputation authority called The Campaign Registry. The registration requirements apply to 10 DLC messaging (10-digit long codes), otherwise known as US local phone numbers. There are fees associated with registration.
Phone.com has provided these instructions to help you
If you need further assistance, please contact Phone.com at 877-746-6310
Some questions you will be asked about what message will a customer see when they message you. You can test these by sending your self the text message. Here are the pre-programmed responses from AllProWebTools: