Charged for Modem Rental when we have our own.

I recently had a tech come out to my new apartment and in the mean time we have been using internet that our landlord had setup before we arrived and she said we could use. After ours was setup we are still using her modem&router until ours arrives in two days. For some reason we are being charged an extra $14.00 on our bill for a modem rental fee. I have tried to find a number to call but for some reason the bot only shows me the breakdown of my bill and not how to fix it so I am posting here. Hopefully someone from Comcast/Xfinity can respond to this.