If you didn't know it. In some online messengers such as AIM and Yahoo. They can send you SMS text messages to your mobile phone number. You could receive spam text or text from an annoying Ex.
Fear not though. You can easily block them from using these messengers to send text messages to your phone. Here's how.
To unblock someone from sending you text message through AIM. Simply text their username to the AIM Unblock number.
If you do not want to receive any Yahoo! SMS text messages, text "block all" to 92466. (without quotes)
As you can see in the previous image. If you text unblock [username] to the yahoo block number it'll unblock them.
I hope someone finds this helpful.