Why is adding a second back up card on Xfinity Now Such a prolblme?

I tried adding a second payment method 50 [Edited: "Language"] times because I want to pay with my Cash App Mastercard. When I added the card, my original card I signed up with disappeared. Then I tried over and over again adding the card and I get the message below. It's not there. I check and add and check and add. Then I try explaining this to your WORTHLESS customer service. I finally tell them to please give me a number to call to just pay my bill. I am not going to do this with the chat ever again. Then when I get someone to call me back then are in Xfinity and not PREPAID. I had no idea when I signed up I would get this form of Xfinity that has even worse customer service that I couldn't get any worse. Was wanted to turn my old comcast account back on not this [Edited: "Language"]. But here I am. The people on the phone bounce me to PREPAID and they tell me they can't accept payment over the phone and coax me to get back on the chat. I am like are you kidding me?? Then I get someone else on the chat, my 3rd person because the first one dropped me to another agent. Then this woman calls me telling me she is not the original [Edited: "Inflammatory"] that told me to go back to the chat. She tells me ok we do have a phone payment service and if it doesn't work I will call you back. This service then tells me both of my credit cards are on file even though your [Edited: "Language"] app tells me I have no cards on file at all. [Edited: "All Caps"]

Then more calls. Then more agents. I am telling you right now I have the 3rd person on my chat after I requested an upper level management complaint and I was waiting for a complaint ticket. Then I get no ticket after waiting 15 minutes and I say OK? and another person in the chat appears. 

I would rather pay twice the amount just to get a competent person on the phone and if I know I was going to get a cheap [Edited: "Language"] service from Comcast I would have never signed up for this nonsense. Why [Edited: "Language"] is your app so [Edited: "Language"] that your system has both of my payment methods, I need to pay my bill and I was looking to pay it a couple days early and now it's me trying over and over again just to pay my bill and this is total nonsense. 

I am not in my 2nd hour of trying to get a [Edited: "Language"] complaint ticket to ask someone in the USA what [Edited: "Language"] you did to me. I would have never, ever, ever signed up for this service and asked for the original one but your entire thing was misleading. $45 is a good price but I can't even get anyone to give me anything but "Oh sorry sir you are in the wrong department let me transfer you and now you can't even pay over the phone or trouble shoot your [Edited: "Language"] app. I want to complain that I was misled into a really [Edited: "Language"] version that gets me zero coorperation and the worst customer service I ever had in my life.