Hello & Welcome to Just Answer,
Sorry I didn't see your question earlier and to hear of any issue you are having with your phones.
To help you with this issue, may I ask:
1) How many TOTAL cordless handsets do you have with this system, and if more than one, does this ECHO sounds happen one ALL of the handsets?
2) Do you hear this same echo when the MAIN BASE UNIT is used in "speakerphone" mode?
3) What phone service provider (phone company) you have for this phone line?
4) Do you have ANY other devices (phones, fax, alarm system, etc.) attached to this same phone line and if so, are they working properly (without the ECHO sound)?
I see it has been a few days and I just wanted to follow up to see if you have any more questions concerning this issue or if the issue was resolved?
I look forward to any further questions or results that you may have.
Thanks, ***** *****--. .-(im)