Samsung Galaxy Phones losing Mobile network while on Wifi

A

AC Question

So I had a Galaxy S4 with Sprint and every time I'd connect to Wifi my mobile network would lose connection, so I wouldn't receive texts or phone calls, and at the time with Sprint I could use Google Voice for texts. Eventually even when not on Wifi the phone would lose mobile connection, I would have to restart my phone 5 times a day (putting it into Airplane mode and back out of Airplane mode wouldn't work) Also I would remove all cards, SD and Sim, then reboot and still after an hour or so I wouldn't have service.
We'll now that I switched to AT&T I have the Samsung S5, and I notice, it too is now losing the Mobile network while on wifi, having the same issues. Fortunately putting the phone into Airplane mode and then back out of Airplane mode works, it seems once the mobile network sleeps, Then it cannot reconnect. And now for some reason I cannot use Google Voice for texts, it only does Voicemails and phone calls. did some searches about Google Voice and found a lot of people having this issue when they ported there number from one service provider to another. Most said, you may have to wait up to 3 weeks for texting service to take effect after a Service Provider port. Well its been about a month and still no Text feature, not on the phone or Computer Via Google Voice

Is there some app or setting that will keep my mobile network active while I'm on Wifi

and What the hell is up with Google Voice, is it because I'm not with sprint anymore, is why I cannot use text via Voice? or is there a setting Im missing.

Now that I think about it, I had this same problem with my Motorola Photon with Sprint as well. Maybe its just me, I find that if Im in a rush or a little frustrated while on my phone it seems to work less, which makes me more frustrated, which makes the phone work even less... Vicious cycle. Maybe I put off some electric field that screws with electronics. My Computer and old iPhone did the same thing....

Any input will be appreciated