I'm trying to sort out a problem with my Father's Motorola Defy+ where during a call, the callers claims that their voice is being echoed back at them. Seems to have started in the last week, prior to that, it was fine (have made calls between us several times before using the same handsets).

He has rung me on his phone (Defy+) and can confirm that what ever I say gets echoed back at me at full volume on my Xperia Acro S.

We have tried reducing the "in call" volume to the lowest setting and the problem continues to persist.

I've have attempted a master / factory reset on his Motorola Defy+ (Holding down the power button + Volume down --> Cleared cache AND then "Wipe data / factory reset"), and without setting up any accounts what so ever (leaving the phone as bone "stock" as I can keep it) and calling my phone, the echoing problem still persists while in a call with his Defy+.

Is there anything else I should try before I suggest to him getting himself a new phone? Cheers.