No call back - issue with billing

So I spoke with "Maura" last week, who promised to do some research and call me back (and I specifically asked her not to blow me off, since other comcast service people have done that over the years).   And yet, no call back.

I've been getting charged $15/month for a piece of equipment that was taken back by one of your on-site technicians almost a year ago.    I'm embarassed that I didn't notice the charge until recently - my bill is over $220 each month, and I probably cringe even thinking about looking through the bill.   Anyway, she confirmed, on the phone, that they did, in fact, have the wrong information in my account - AND that I WAS using my own cable modem.    She said it should be straightforward to get the credit applied to my account, but would just need to speak with a supervisor and get back to me.   She said, "It will probably be before the end of the day, but absolute latest by tomorrow morning".

Nothing for over a week.

Can you please let me know what's going on - so that I don't keep getting charged each month for something I don't have and don't use?

Thank you

Tom