Echo voice on MX4 pro

Hello,
Sorry for my English.
I bought Meizu MX4 Pro Chinese version. Before inserting sim card and test I changed software to 5.1.8.0G. Now when I call somebody they say can hear echo of their voice as they speak, but everything sounds normal on my end. When I go to loudspeaker or viber call everything is ok and no echo.
Can you help me?

@Тихомир-Ботев I had the same problem and the problem was the case of the phone. without the case i have no problem

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