Feiteng H9500 bad mobile reception

[fronimitis]

I bought Feiteng H9500 back in August, it had problems (volume down and soft keys not working) so I sent it back for repair. Now that it has returned, repaired, I see another problem: The reception of the mobile signal is awful and the phone is practically unusable as a phone. It didn't have this problem the first time I had it. The signal bars sometimes are not stable (while staying in the same spot), sometimes they show 4/4 signal, others 2/4 and other times the phone is searching for network without finding anything. (For comparison, other chinese phone with the same SIM/provider shows 4/4). Especially indoors, it's almost impossible to get reception (phone is always searching). On top of this, sometimes even when the phone shows signal reception I cannot receive any phone calls or SMS ("subscriber not available").

I wonder if it is a problem of the bad antenna but in my case Wifi and GPS reception work decently.

I still have warranty from the china seller, but I don't like the idea to pay another 15 euros to send the phone back to them and wait for almost 2 months to get it back. I am thinking to make the antenna hack myself (voiding the warranty, I guess), but I am not sure if it's really an antenna problem or other hardware problem. I am also thinking if I should sell the phone at a low price only as a game machine or mini tablet or whatever.

Any suggestions?

[tiefighter_85]

Maybe its some ROM problem? Is it different from the first one you had?
Maybe antenna. Mobile network antenna is 3g one.I think different from GPS and WiFi ones. So possible just antenna.
Try pressing the part where mobile antenna is? Before opening.
Other hardware also possible. See Sim tray. Maybe
Sims don't fit well and lose contact.

[fronimitis]

Thank you for your reply. I couldn't figure out the problem, so I sent the phone back, again. I already have it back, I don't know what was fixed. It's working... for now...