about pepkoo casing
I've using my pepkoo casing around 2 weeks.
Everything's in good condition and I could hear any caller's voice very well.
Sadly, there's a problem when I tried to make for call out to friends.
It seemed they can't hear my voice clearly.
For some other reason, it has an echo sound of my own voice.
What's happening here?
May be because the type of waterproof casing?
Does anyone has any opinion on this issues?
Thanks so much.