Hello & Welcome to Just Answer,
I'm Greg and will do my best to assist you today.
Sorry I didn't see your question earlier and 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? If this is a cordless system, that model should be printed on a sticker on the bottom or back of the MAIN base and START with KX-TG.
NOTE: The MAIN BASE will be LARGER than any "remote charger", and will have a phone cord and power adapter connected to it.
Perhaps you missed it, but a model number for a Panasonic phone SHOULD be a in a format that STARTS with the letters KX-TG. AND then there are usually 3 or 4 NUMBERS - after the letters.
Unfortunately, I'm not finding a "64828" number sequence.
Could that actually be something different, as I know the model numbers are usually in smaller print, and sometimes need to be MAGNIFIED to see the entire model.
Please let me know if you can find a model that matches the stated format.