Charged the High Speed Equpiment Fee despite using my own previously purchased equipment

I had Att Uverse internet service a couple years ago, and when I signed up back then I had to purchase a $100 modem as part of the service. I've moved around a couple places since then and haven't had the service for some time. I recently signed back for internet service. In the process of signing up, I asked about this High Speed Equipment Fee, and was informed that if my old modem still worked I would NOT have to pay the $7 a month. The install tech supported this line of thought, and fortunately the older modem still works fine.

All was good until the bill shows up with the $7 high speed equipment fee was included. Remember, there is absolutely NO rental equipment in my procession, I own the modem currently in use. I hop on the support chat, the rep seems to understand the situation but is unable to correct the issue. I then call in, the rep I talk to again seems to understand but says there is nothing he can do about the fee. He claims that even his supervisor is unable to correct the issue. I asked to speak with the supervisor anyway, and end up on hold for over an hour with no response. I was told the supervisors name was Oscar.

I'm quite upset about this, because it's appears to me now that I was lied to by the sales rep and then completely ignored by the support supervisor.

This post here describes a similar situation and confirms that I should not be charged the fee:

https://forums.att.com/t5/U-verse-Account-Questions/High-Speed-Internet-Equipment-Fee/td-p/4013050

Is anyone on here able to help me correct this situation?

Thank you!