Can I Use My Regular AT&T Phone Service And A Voip Phone In My Home At The Same Time?

I have had U-verse 450 for appx. four years, in addition to AT&T Internet, home phone and a five line cell phone service. I don't watch TV but I subscribed to the U-verse 450 so that My Chinese wife and stepson could improve their English. I cancelled the U-verse 450 part of my bundle because they no longer need it but I still have my  home phone, Internet and cell phone service, all provided by AT&T. When I cancelled my U-verse service I returned the receivers, remotes and the wiring. My modem/router (3801HGV) and battery did not have to be returned so it remains the same.

I have Dish TV with the Great Wall package so that they can enjoy many Chinese channels. I didn't go with Direct TV for the Chinese channels because Direct doesn't offer any good Chinese packages. I am now going to cancel my Dish TV service because I have decided to go with italkbb, which offers many more Chinese channels at a substantially lower price.

Now, for the meat of the matter. I want to retain my AT&T landline phone while also using the italkbb VOIP service so that my wife and stepson can have their family members and friends in China call them here in the U.S. free of charge and vice-versa using the italkbb VOIP phone. I don't think I'll be violating any of my AT&T service terms. I use a three phone Panasonic 6.0 plus system for my AT&T home phone service and I have my older Panasonic three phone 6.0 system that I will use for the italkbb VOIP phone service. I may be wrong, but I assume that my AT&T home phone service coming through my U-verse modem is not VOIP because I have the Linebacker service for it. The italkbb VOIP phone service will plug into the italkbb box, which will connect to my AT&T 3801HGV modem through either Ethernet cable or wirelessly. I haven't decided yet which way to go.

Is it possible to have both services in my home at the same time? That is my question. I would certainly appreciate any feedback from those who have the knowledge pertaining to this matter. Thank you in advance for your time and any assistance provided.