How do I switch inputs using the AT&T Remote?

Mine works like you said except when I hit the OK button it changes my TV input the the one selected by the input button. 
Not sure if it will help you, but my remote was only controlling certain functions, so I  put in new batteries and it worked correctly. One battery was good and the other was almost dead.

When your remote is programmed to the TV, you will be able to turn the TV ON/OFF, control the volume and change the input. Each TV manufacturer is different. If your TV requires you select 'Enter' or 'OK' for the TV input to be selected, you'll have to use the factory remote. Jamie, DIRECTV Community Specialist 

So, me just thinking... it used to be, if you wanted the ultimate remote to control everything and have it work flawlessly, you bought a logitech harmony remote.  But, Logitech stopped selling them.  It seems because the universal remote is obsolete with the whole streaming world we're in now.  I think the whole objective of the new media center is you have your TV and a streaming media player.  Nothing else.  Your one remote should control both.  But, the future of reverting to a pocket on the side of the couch with 7 remotes in it doesn't seem like forward progress in the way of home entertainment.  

There is a universal remote I did find that is similar to logitech, but it doesn't work nearly as well.  It seems like it's a dying market because people are switching to solutions that you don't need it.  Begs the question what am I doing wrong here?  I think part of it is disabling the CEC on the TV... because the TV is messing up with it on.  But, I work in technology as an IT engineer.  My job in my professional life is to make a solution work.  But, it has to work right.  It can't look and feel hodgpodged... and having multiple remotes feels hodgepodge.  There has to be a better way.  And my not settling for the way it is is the way it has been, is, and always will be, and instead assuming there has to be a better way is what makes me good at my professional life as an engineer.

Which "similar to logitech" remote did you find?  There are several (at different price points) that offer (or claim to offer) similar types of functionality. 

There are a few that are highly regarded but are very expensive - they are available only from "home theater" dealers, and you have to be in a higher tax bracket than me to deal at that level.  The MX990 is an example.

Lower down, there is the Sofabaton X1, which is probably the closest to the Harmony Hub models - not (yet?) as solid, but mostly liked and hopefully continuing to improve.  Then there are some hub based units that don't have "remote devices" but just use an app on a phone to control the hub - an example is the Broadlink RM4.  There are also some standalone (non-hub) remotes that claim to support Harmony-like activities.  I don't know how good they are - the Sofabaton U1 didn't do it for me, but I've just learned about the Flirc Skip and may give one a try.

So, the reason why I'm trying to get the original remote to work is, the only thing I need the other remote for is to switch the input.  The Sofabaton remote I have works... sort of.  But, with the Directv receiver, it's weird.  When you're using the menus, it double pushes buttons.  It's super annoying when you're moving over one item in the top menu and, everytime you hit the button once, it moves two items over.  It kind of works randomly like one click, two jumps, one click, two jumps, one click one jump, etc.  So, I usually have to go back and forth a few times until my one click on the remote moves it only once so I can then select what I want to select.

I emailed support and they said they weren't aware of the issue.  They asked me for the model number of my directv receiver so he could order one and try it out for themselves.  With the logitech remote, there was a setting that I could adjust for issues like this where I think it shortened how long the command was sent to the TV.  the original remote works so much nicer than the sofabaton.  I don't like that hub thing that I need to always keep in clear view of the TV.  It's annoying.  All of the annoyance so I can just change the input once in a while.  All of it is for the Xbox and I don't even ever use it.  Only the kids play the xbox. 

When I hit the input button on the Dtv Stream box remote----If I go to the input I want---then wait a few seconds my Samsung TV changes to it and I don't have to do anything else.

I tried just waiting after I get to the input.  My TV doesn't work that way.

Do you have hdmi cec enabled on your tv? If you turn on the stream box---the tv should change to that input automatically if that is enabled.

I've purposely turned off CEC.  CEC is messing up which led me to this whole issue in this thread.  With CEC enabled, the TV in recent weeks started messing up all the time.  You'd turn on the TV, the TV would have picture but no audio, then the picture would turn off, then audio would start playing, then it would all go black. Then the TV would show it's off, then it would turn on and then after so long you'd see picture and then sound and on and on and then, if you waited about 30-45 seconds or longer, it would start showing correctly.  Sometimes I'd have to turn everything off manually.  Sometimes that would fix it.  Sometimes I would have to completely unplug the TV.  It was happening constantly.  Turning off CEC fixed that issue.

What brand is your tv?

Hisense.... don't know if that's the issue.  It was a cheap tv off the endcap at walmart.  My wife wanted a new tv.  I was perfectly satisfied with our 55" samsung.  But, in all reality, it was too small for the spot where we put the tv in our new house.  But, I'm the person that, if I'm buying something, I go all out and get the best or more than we can afford.  My wife, on the other hand, if she can save a buck, she will... we don't need the best all the time.  So, she was with me.  She won that battle.  Im not a audio/vidophile person necessarily.  I like a good surround sound.  But, if you were to have me do a "blind" audio test between a $500 surround sound and a $5,000 surround sound, I probably could tell the difference, but maybe not.  I'm sure I can tell the difference between a $50 surround sound and a $500 surround sound.  Same with the TV.  Picture quality between a $400 70" Hisense TV and a $5,000 namebrand TV, I probably won't be able to tell the difference.  So, it's fine.  But, wonder if that's why the CEC is flaky,.