Talking probleme

May 2, 2013
Hello i just bought yestarday my xiaomi mi 2 from *******.I have a probleme with my phone:
I downloaded the latest ROM 3.4.28 and all updates.
But i have this probleme: When iam talking voice are fading i cant hear anything for some seconds after this (sound-voice) coming back and then again not sound.And when iam typing a message i dont have all Letters on my keybord and typing some letters like (O) its goes on gube on my screen ! pls help me is my phone probelem needs replacement or its programe probleme (ROM) . I send my probleme 1 day now,to the site i bought it but they dont aswer me nothing.