Services keep getting turned off for no fault of my own

I set up an installment plan on November 6th so everything was split into 12 payments and would be added to my future bills. November 16th my bill comes out and you can see plain as day in the PDF file of the bill that there is NO past due amount and no balance forwarded and the current bill is due December 11th. Why have I had to call everyday since December 7th because they are turning off my services daily then? I was told it's a glitch it their system stating that a $43.70 charge is past due 55 days (what?!). I was credited that charge as it wasn't supposed to be there yet still had to call today to get my services restored. This is interrupting my day and life and my income as I work from home. Calls to Xfinity have been anywhere from 20 minutes to an hour. How do you expect me to keep paying my bill if I can't make money to do so? My current bill is $223 and some change although when I called to get it restored today the lady told me it was $230 something and could not explain why it had gone up. I have been a loyal customer for over a year but I am starting to question it now.