If an employee doesn't help you here, contact one of their Billing reps and have them reverse the charge. Call them at the phone number on your bill or 1-800-Comcast, chat with them using the "Billing" option at https://support.xfinity.com/chat, or visit a Service Center or Xfinity Store if one is nearby (check locations and hours at https://www.xfinity.com/support/service-center-locations/).
In addition to getting the billing corrected, consider setting up a Purchase Pin on each of your cable boxes/DVRs and in the Stream app and web portal to prevent this from happening in the future. See https://www.xfinity.com/support/articles/how-to-block-purchase-of-pay-per-view and https://www.xfinity.com/support/articles/x1-parental-controls-turn-puchase-protection-on-off.
Welcome to our community, highsmi4! I can help you with the accidental On Demand purchase. Please send me a private message and include your full name, the account holder's name as it's listed on the billing statement. Click on my name ComcastElla, then click Send a message.