echo noise thru radio

Hey guys I installed a jvc kd-bt11 in a 2007 toyota sienna unit worked good no problem but now the unit when the customer gets a call or calls out the person on the cell phone hears an echo. I turned down the mic and radio volume but he still once in a while gets that echo that is heard by the person on the cell phone that calls him. Is this normal for these units? thanks.

if you install the microphone in the guage cluster the echo should stop, if you do not have the mic installed there i would try putting it there, and if there is still an echo typically the unit should be replaced