forward txt message from a line number to another one under the same account

It is obnoxious that the support documentation for reporting a SPAM text message says clearly, FORWARD THE MESSAGE TO 7728 (SPAM). It seems counter-intuitive that you can't forward a message. This should be easier

As far as I know, there is no way to forward SMS/MMS messages.

Digits would allow you to receive your texts through a computer instead. might be a better route for you to take.

Agreed Jaseinati, unacceptable!

It depends on your messaging app. If you long press on the message a menu should open that gives you the option to forward in Google messenger. It doesn't give you that option in Textra.

Gramps28 - for myself ( and I think Jaseinati ) it's not an issue of forwarding a single message. It's an issue of having ALL our text messages forwarded all the time. 
 

On the upside, if you have an iPhone, you can at least set up an auto reply by going to focus and adding a driving focus, which allows you to at least send an auto reply to text messages. That's what I'll end up doing, not ideal but at least it lets people in my contacts know that I'm not ignoring them. Not sure if other devices have a similar setting or not. 

Have you tried the Play store? There's some 3rd party apps that may do what you're looking for.

I’m iPhone so it’s the App Store, however, there was nothing I wanted to pay for so… thanks for the thought!

Plus, I think those must be active to work, in my case the phone will be turned off…

Check out the XDA forums , they may have an answer.

But I agree with a previous poster suggesting Digits.