question

I work as a Client Care Coordinator for a real estate company in the US and I downloaded Ring Central to have the ability to text people back from my work phone so as not to have to give out my private number. Everything has been fine. I was receiving and sending text messages with no problems last week. This morning though I am unable to reply to a text message i received. When i try it tells me a valid phone number is required to send text messages to recipients outside my company. What happened? Why can I no longer send text messages and how do I fix this? It is a very important part of my job to be able to send messages back.