I borrowed a voice enhanced 5.8 GHz cordless phone from work and the echo was better but did not disappear. I have to try the recommendation of changing the router from the D-Link to a Linksys. I will try that and hopefully that will work. If not, than I am at a loss and will have to speak to Fios tech support again.
I also have called Verizon with a similar echo and very loud sound. This true with regular verizon phone service and my recent voicewing. VerizonFios tech support determined that my phones are not compatible. I need to get a phone with voice enhancer and disable it. I will try this and if it works, I will report back.