Hello & Welcome to Just Answer,
Sorry to hear of any issue you are having with your phones.
To help you with this issue, may I ask:
1) The FULL Model Number of the phone system you are working with? That model should be printed on a sticker on the bottom or back of the main base unit and START with KX-TG (but no "A").
2) How many TOTAL cordless handsets do you have with this system?
3) What "remote access code" are you trying to change and what happens when you TRY to change it?
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)