Hi, I'm Nathan.Sorry to hear that you're having trouble with this but I'll do my best to help you.
This is more likely blocked on the panasonic than through ATT.
Pick up a handset, and key in Menu#217
This brings up the blocked call list on the panasonic,
upse the up/down arrows to scroll though the list until you get to the bosses number, then press the ERASE button just below the screen,
up/down to YES to confirm
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Thank you, ***** ***** a nice day,
Yes, but I need to know specifically where you are getting stuck.
When you followed the above, did you see the number in question in the list?