Where could I file a compliant? Got yelled at by a Customer Rep

This is the first time I’ve felt compelled to make a complaint, but the level of services I received was unacceptable. The person who assisted me today at the store yelled and me and was very condescending through the whole experience. I have decide to switch to another carrier because Xfinity charge an extra 25 per line when you don’t have WiFi service with them. I came in to the store and request a final bill, if that is unavailable, I just need a statement showing the balance of the remaining balance on my phone. The representative who assisted, named Derick, was unable to provide the information and offered no alternative solution. Simply told me that he cannot see this account and mentioned that the billing team might, he did not communicate to me well but just went ahead and put me on the phone with the online team for two hours, who also could not provide any information. I am frustrated at this point, I don’t understand why no one in the company could provide any detail/ statement on the remaining balance. I asked what services could the store assist me with, he repeatedly told to just check the app, without making any real effort to help. I know the information that is offered on the app but that’s not what I need. I am trying to ask what they can do, before I finish my sentence, he keep interrupting me, and I had to repeat could you please listen to me and stop yelling at me a few time. Throughout the interaction, I felt that Derick was dismissive and unprofessional, and I felt that as. Non-native English speaker and as a women may have played a role in the way I was treated. Since there is no information I can get from this, I just want to leave but asked one last question. When could I get my final bill, first he mentioned he could not speak about this information, then change the whole story and told me he has mentioned to me 2 hours ago that it will be available in the app within 24-48 hours after cancellation, and claimed he had already told me that. He made it sounds like it’s my fault for staying here trying to get it figure outed. Still, I don’t have the information. Not to mention, the reason why I came to the sore the first place is because I chatted the customer service earlier, they told me the store can print it for me, however, when I told Derick that, he said the representative has lied to me. I am unsure who is telling the truth or he just unwilling to help. I felt being disrespected for the whole experience. And I would not recommend Xfinity to anyone, because you are likely to deal with CR like Derick.