Let's see what we can do to resolve this. You get that error if for some reason you are not able to access our network. This can have various causes, so please allow me to ask you a few more questions:
Are you connected to an Airave device when trying to send the text message?
Were you trying to send a MMS? (picture etc)
Can you give a zip code and cross streets?
What type of phone do you have?
Have you tried to update your data profile and to powercycle your phone?