Well, I don’t know, but I can do it. With my computer, I can sign onto my phone company’s website using my phone number and use its text function to send a message to someone’s cellphone. If I hadn’t stumbled onto that accidentally, I wouldn’t have known about it. I can also send a text message from my phone to someone’s e-mail—usually my own, because this is how I send myself reminders. So your contacts could probably do the same with you.