If you've ever tried to send a text message and seen the words "free message, unable to send message blocking is active" appear on your screen, you may wonder what that means. Message blocking is a feature that allows you to block unwanted texts, calls, and data usage from certain numbers. When message blocking is active, it prevents the person you've blocked from being able to contact you. There are a few different ways that you can block someone's number. You can ask your cell phone carrier to block your number. Most carriers will do this for free. You can also download an app that will allow you to block numbers. Some of these apps are free, while others charge a small fee.