Voice echo on speakerphone during calls

Okk so i am having this really strange issue that whenever i call someone and put my phone on speaker phone
i am hearing echos of my own voice. i have already tried to wipe cache/delvik. :(:(:(
i just want to know that is it a software issue? Or is it hardware? I really dont want to send it back. :rolleyes:

How do I stop the echo that everyone else hears during phone calls?

I can only stop the echo by using the speakerphone or earphones. Is anyone else having this problem?

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