I bought my own modem and xfinity changed my contract without my explicit consent

I was in a triple play contract with xfinity that still has some time on it. I do not and never have used the voice line that's included, but agreed to the package because it was cheaper for our use case than similar plans that didn't include voice. I was renting an xfinity gateway, but opted to buy my own modem and router a couple weeks ago. The modem I bought does not support voice, which I was fully aware of, but I don't care because I've never used the voice line--I don't even own a landline phone. I activated and called xfinity to remove the old gateway, which I sent in via UPS. They sent me a link to my cell phone to authorize removing the gateway and seemed to be all set--I was told my modem was compatible, and my service has been great.

This past Thursday April 15th, I missed a phone call and had a voicemail. The person identified themselves in the voicemail as "JR" and said they were calling regarding an "equipment discrepancy" on my account. I called back 1-800-COMCAST the same day and the representative told me he had no record of the call. He then conceded later in the call that it was likely about removing the old modem from my account, which I had already sent back via UPS and authorized. He sent me a link to authorize removing the gateway, which I had already done when setting up the new one, but that was fine. I reauthorized removing the gateway and figured I was all set.

Yesterday, April 21st, I received another call and voicemail while I was at work saying it was "JR" again and this was their "third and final attempt" trying to reach me in regards to the "equipment discrepancy" on my account (I had only ever been called twice?). He then expanded this time and said "please be advised at this appointment time we do need to remove the landline phone."

I called back xfinity today, April 22nd and was told that because my new modem doesn't support voice, my plan was changed to a "double play" plan with slower internet speeds. I explained my situation thoroughly and told the representative that I never authorized any change in my plan--I was in a contract, why would it change? She told me that no changes would ever be made without my explicit consent and kept repeating this, but I never gave my explicit consent. She then quoted me what this new package would cost, and it was more than what I was quoted in an email after removing the gateway.

To summarize:

-Comcast told me my equipment was compatible and service has worked great

-Comcast called me to ask about an "equipment discrepancy"

-I called back and the rep didn't know what phone call I was referring to and reauthorized removing the xfinity gateway from the account

-Comcast called again to tell me again about the "equipment discrepancy"

-I called back and am being told my plan is now changed to slower speeds without voice for more money.

I don't care if I'm being charged for the voice and not using it. I don't own a phone and never hooked one up when I had the voice-capable gateway. Why was my plan changed without my explicit consent, particularly after the rep I spoke with on 4/15 had no record of the call?

The rep I spoke with today was supposed to call me back at 12:45, but still hasn't yet. I am awaiting a resolution.