I suggest you find Panasonic's phone support for your country and call them.
http://service.us.panasonic.com/OPERMANPDF/KXTG7622-MUL.PDF on page 94 has service contact information.
"Your cellular phones must be Bluetooth
wireless technology compatible with this
If it worked before and Apple updated the phone, it is possible it is no longer compatible. Panasonic may know this.
I had to replace my iPhone 3GS so I am reconnecting all of my Bluetooth devices, except the Panasonic wireless 4 phone system which is giving me problems. Since I have reconnected other devices I don't think it is my iPhone.
My wife's iPhone is connected and I disconnected it and it reconnected without hesitation.
I enter the Bluetooth menu of the iPhone where the devices are listed and it is "searching". In the Panasonic phone I go in the Menu to the Bluetooth menu and select my line that has my iPhone still listed on Line 1 and I select "Connect". The yellow light on the Base Unit starts to flash indicating it is in the paring mode but the device never shows up in my list of devices on the iPhone.
This is where I am waiting for some help.
Thanks in advance.