Billing Assistance

I was being billed for TWO phone lines for my business since my account was opened over a year ago (we only have ONE LINE, which Xfinity confirmed).  I realized this billing error a few months ago, and I was told it would take a few weeks to see a credit (estimating about $360 PLUS TAX).  That was about 2 months ago.  I called again about a month ago, and was told it would take a bit longer to get my credit.  Now, we have not been at work for about a month now because of COVID, but I can tell by my security system that our Xfinity has been turned off.  My amount due is currently showing $500+.  I tried calling Xfinity Business today, and you are closed!!!!!!  So, you shut me off and give me no opportunity to speak to someone to get it turned back on.  Anyway, my minimum payment was $327.50, which I just paid (confirm # 7930206951) -- which is much more than the $140 that it should be!!!!  At a time when money is very tight and the whole country is struggling with no income and no revenue, this is what I had to do!  So, what does it take to get a credit for the year of erroneous charges ($29.95/month plus tax) that I've paid credited back to me?  How much longer am I supposed to wait?  You want your $ from me and you shut me off, but I want MY money from you!!!!!  This is very stressful and frustrating.