please note signal is ok, may phone dialer app has problem? how uninstall/install default dialer app?
My Android phone has problem... In the start I bought it no problem but after 2-3 panels (now have 5 panels) of Apps installed appeared problem below... is any possibility of a virus?

phone: global samsung Note 2.3.6

problem: after pass half a day or one day device lost signal and needed shut down and restart to find it(same area). Main operate area 2.5G sometimes 3G.

SIGNAL BARS continue to show has signal but after try make a call a message appear: "Mobile Network not available". I can not also receive...calls...

Other phones/smartphones have no any problem, same area.

changed sim, same problem.
insert a new sim, same problem.