Cisco DPC3825 and iPHONE 4S can only log onto wifi with Out of the box SSID and Password

Model:     Cisco DPC3825
Vendor:     Cisco
Hardware Revision:     1.0
MAC Address:     
Bootloader Revision:     2.3.0_R3
Current Software Revision:     dpc3825-v302r125573-140516a-COX
Firmware Name:     dpc3825-v302r125573-140516a-COX.bin
Firmware Build Time:     May 16 11:58:28 2014
Cable Modem Status:     Operational
Wireless Network:    Enable

Since I set this up I have not been able to get my iPHONE 4S to connect to wifi UNLESS I reset the router and leave it with

the generic User Name and Password settings. I have tried 6x to change name/pW but No Go.

Also the 1st time I set it up I had to reset it because it did not recognize the password even though I had a screen shot so I am Certain I input it correctly and right now I see that again the New name and PW I setup yesterday and successfully used to log on to router is now not recognized.

So I need some assistance please. It was suggested that I got bad unit from COX

Thanks