Z5 Premium Call Echoing Issue

[5ilver5tone]

Had collected my mobile phone 3 weeks ago on warranty repair due to unable to power up. Was informed during collection that the motherboard has been replaced.
But now I have issues making calls as the called parties are not able to hear me (echoes) and loud feedbacks.
Please assist to resolve this problem asap, thks.

[Qatrium]

Hello @5ilver5tone and welcome to the community!

Usually echoing sounds is an operator-related issue, and if you can try a different SIM in your phone to exclude this probability. But if you think it's related to the last maintenance process, then you should contact your Local support as soon as possible and make a complaint about it.

[Sox1]

I have the same issue of echoing,  this only affects the person I'm talking to and not myself, whether I make or receive the call. I have changed the sim card as suggested above and can confirm that this does NOT rectify the problem.