it is probably the phone. My first smart phone was a G Ace. Initially the internet was poor on the phone network but not having had a smart phone before I didn't know what to expect. I put it down to phone coverage in my area. It was fine for browsing when on WiFi and I had very little phone call usage. When I started to use it for a few phone calls I found that it would drop calls repeatedly both around home and further afield. Then I noticed that the signal strength displayed by the phone was going to full for a few seconds and then dropping down to nothing over a few seconds and then jumping back to full. It was doing this all of the time. I took it back to CaonWarehs and showed them the issue.
They sent it off to their repair shop where the fault description was ignored, the phone reprogrammed, given a cursory test and shipped back to me. On receipt the problem was just the same so as I was already at CaonWarehs I showed the shop staff the problem, filled paperwork etc.
After it had been back to the repair shop for the fourth time I lost my temper with the whole outfit and demanded they do something different. CaonWarehs started to blame Samsung for the problem and Samsung told me it was the CaonWarehs repair shop ineptness. Eventually they exchanged it for an HTC Desire S which my partner still uses as I had bought another phone in the meantime.
Good luck,
Rans6......