[Question] Problem in 3g mode

[alekosal]

I 've recently came back to Greece from a trip to Spain. When i try to speak with my phone (zopo zp 980) to another chinese brand phone, there is a noise in the line that made the communication very difficult. There is no problem when i speak with no chinese brand phones. Also there is no problem in 2G mode or in 3G when the phone charging. Does anybody haw an idea about that?