I have this issue as well, where the phone seems to disconnect from the tower.

In my apartment with the stock Sprint radio I have 0-2 bars of service... This just isn't right because my Helio Ocean (which is AWFUL for radio reception) gets 4/5-5/5 in the exact same locations. I switched to a different radio and I get 3-4/7 now, which seems ok, but this is what I have noticed.

When signal is poor (as if 3 bars with 3g can be called "poor") the phone will tend to disconnect from the tower. Calls, texts, and other 1x transmissions (voicemail notification, etc) will not come through in this time... It's like the phone stops polling the tower. To correct this, call your voicemail and wait 20 seconds, the texts will be pushed through, and calls will work again for a while - at least until the phone disconnects from the tower again.

I have made a habit out of calling my voicemail all of the time, if you look at my phone bill I have about 3x more calls to my voicemail than I have incoming/outgoing total... all of them 1 minute (about 20 seconds, to be specific) long. This is the only way I have to get my texts pushed through and make it so I can receive calls. It's only like this in my apartment, which really sucks. Other places I'm moving around so signal goes up and down and calls and texts will come through, but when I'm here it's nothing, and it's very frustrating.

Edit: Forgot to mention, Helio is a Sprint MVNO, so my main reason for switching to Sprint is I knew I'd have excellent service in my new apartment... but I guess I was wrong.