Cannot connect to apppstore

Recently I took my phone to the Apple store. The Genius had the phone wiped clean of all data and apps, and performed a new reinstall from my iCloud backup.

Within a day, most of my apps will open, but do not respond, the sound is close to inaudible and the phone takes about 18 hours to charge.

I went through the procedure again a few days after I had taken the phone to the Apple store and I still get the same results. Is my phone dead? Is it salvageable? I’m kind of at a loss here as far as what to do besides just give it back to the Genius Bar people and buy a new phone. What do you think I should do and has anyone else encountered this problem?