Getting AT&T Messages app working for two different lines on same account?

[TWC42]

Getting AT&T Messages app working for two different lines on same account

Recently, I enabled AT&T Messages backup on my LG G3 and then put the Messages app on my PC and Samsung tablet. Works fine. Syncs perfectly for whatever I do on phone, tablet or PC.
So I tried to do the same for my wife's HTC One (M7). First, I had to download the AT&T Messages app to her phone and set it up as the default texting app. No problem. It's very similar to the native messaging app.
Then I downloaded the AT&T Messages app to her Nexus 7 tablet (now on Marshmallow) and it asks me to sign in to my AT&T account. As soon as I do, I go to the next page that tells me they will send a text to my "default" phone number, which happens immediately. But it's MY number, not hers, and there's no way to change it. Went through with the setup and sure enough, all MY texts are sync'd to her tablet.
Spent a long time on the phone with AT&T tech support, they didn't have a solution and pointed the finger at Google. I checked, and since the HTC One was previously my phone, the Google account was set up in my name. I changed that, signing in with my wife's Google account, uninstalled everything and started over from scratch. Still didn't help. Same problem, the AT&T Messages app only recognizes my phone number.
On the AT&T website, the page that describes AT&T Messages has a list of smartphones that have the ability to use AT&T Messages backup built in.
http://forums.androidcentral.com/ext...-messages.html
My phone, LG G3 is on the list. My wife's HTC One (M7) is not on the list, but the app from Google has been downloaded to her phone and has been set up as the default messaging app as instructed.
Does all this mean that the syncing will not work if the smartphone is not on the list?
Or am I overlooking something in trying to set up AT&T Messages for my wife's HTC One on the Nexus tablet?
Any ideas will be appreciated.

 

[JMRE5150]

Re: Getting AT&T Messages app working for two different lines on same account?

Did you find a solution to this? I am also having the same headache. Its definitely AT&Ts fault. Why have the app if other family members with AT&T devices on the same plan can't use it to communicate together? How stupid.

 

[TWC42]

Re: Getting AT&T Messages app working for two different lines on same account?

Gave up on it, as my wife isn't interested in seeing her text messages on her PC or tablet. I use it all the time.
She has switched back to the HTC One Mini, I doubt that phone will work with AT&T messages either.

 

[mastaofdacat]

Re: Getting AT&T Messages app working for two different lines on same account

OK here's how I had to do it with my daughter's number on my account ... I created her an att account with her number . No interference with accounts

 

[TWC42]

Re: Getting AT&T Messages app working for two different lines on same account

That should work. I wanted to set up the new Call Protect service on each of our lines, and had to create a separate username and password for my wife to access our account. Then we were able to see our calls to each phone separately.