Bill a closed account

I have 2 accounts with Xfinity. One is open year-round and one is seasonal. I am unable to pay the final bill on the seasonal account on the website, as it no longer appears under "Switch Accounts". I spent over 40 minutes on the phone with support that sent me to the IVR payment system, which told me that I can't make a payment over the phone.

Why does comcast make support so difficult. I know it is to discourage us from using it, but in THIS case, I'm TRYING TO PAY YOU!