SendText and mass alert

Hi,

I have a few Yealink phones and they store dialplan “SendText” messages as SMS messages that can be accessed through a menu.
A want to deliver mass alerts to the phones, but the problem is that ‘SendText’ command only works if it’s channel is active, I mean, only if I’m on a call.

Anyone know a way to do it even with the phone on-hook? It doesn’t need to be yealink only way.