New or old Uniden phone? It's not very likely that a DECT phone will interfere with WiFi; they are on different frequencies as you have observed. Before buying a cordless phone myself, I looked into that.
I have a Skype DECT 6.0 phone and my DIR-655 on the same table; no problems. It's worth a shot to try a different channel and/or shutting off WiFi, because sometimes the things that should not interfere, interfere anyway.

The WiFi settings are on your Router's home page, under the Setup, Wireless Setup, Manual Wireless Network Setup.