My Lumia 520 Suddenly Can't Connect to GSM Service, Why?

[Daigokaujin]

My Lumia 520 Suddenly Can't Connect to GSM Service

My Lumia 520 get a weird problem.
Even though the GSM signal bar is full and show H+, It seems I can't do a phone call, text message, and even data connection.
I try different SIM, but still same.
But If I restart the phone, for several minutes after it's boot to home screen, I can do phone call, text, and data connection.
But after several minutes the same previous problem happen again.

Please help me.
THX

 

[Kunalya]

Re: My Lumia 520 Suddenly Can't Connect to GSM Service

Mee too,from couple of months I am also facing a problem of network coverage I my phone. Tried different sim but issue remains same.