How can I file a customer complaint on overall service at the store and customer service in general?

This is by far the most frustrating time I have with a company who I pay services for my internet and mobile phones for over 7 years. I got back from my Denver trip and my Android phone crashed on me. I tried to reboot the phone but nothing was working and I was due for an upgrade. I tried ordering a new phone through Xfinity's website and they were having a promotion on the iPhones. When I was in the process of ordering the iPhone, I was getting errors with the website and it could not complete my order, so I went to the Xfinity store to purchase a new iPhone 13. The person helping me seem incompetent and didn't build any rapport to see if I was doing fine or acknowledging my presence. The next few minutes of silences and watching him look around and typing stuff on the computer, he acknowledge the phone has been ordered and I should receive the phone in 2 business days. He didn't inform me what my monthly payments are and acknowledge the promotion for the phone. When I got back home, I looked at the invoice through my email and found the promotion was not added to the order and the color was incorrect. During this period, I was not yet frustrated. I called the Xfinity customer service line to see if the promotion was added and if I can change the color to the correct color I wanted. They responded the promotion will be added once the phone is activated and the phone can be exchanged for the correct color. I was fine with that and I had a 2nd line in my mobile account and that phone was also due for an upgrade. My plan was to order the new iPhone 14 Pro with the 2nd line and when the iPhone 14 gets delivered to my house, I would swap the phone numbers from the iPhone 13 (primary number) to the 14 (2nd line) and vice versa. Keep in mind, I pay for both phone services and the phones.

One week has passed and I haven't received my iPhone 13. I knew the iPhone 14 was on back order and there was a date set when the phone will arrive. I called customer service on the status of my iPhone 13 and they informed me the phone is out of stock and they do not have a date when the phone will be back in stock. I've asked them if I can just get a different phone that is in stock but they told me they can't revise or cancel the order because its in process and this is where the frustration gets started.....THEY SAID I HAVE TO WAIT UNTIL I GET THE PHONE THEN I CAN REVISE OR CANCEL MY PHONE! So I then I asked when will I expect the phone and they responded that they did not have a set date but told me to follow up another week. Now we are at week two, I'm losing hope on getting this iPhone 13. I went back to the Xfinity Store to speak with someone face to face to see if they can help. The person helping me was actually helpful and wanted to help resolve the issue. He then informed me he found information the order for the iPhone 13 was inputted wrong in the system and they can't cancel my order. I've asked what can they do to get this resolved and this person was contacting every resource he can find to see if there can be any solution but there was no success and he told me I have to wait until I get the phone. I tried asking for the manager but the manger was too busy with other customers.

At this point, the only option was to buy a new phone but I'm disappointed with Xfinity so I purchased a new phone from the Apple store and paid full price for an iPhone 13 which was worth it because I got my phone the same day I ordered it! Only problem was I had to drive 1 hour away to purchase the phone but I rather support a company that appreciate my business. So we are at week 4, surprisingly I got a notice from Xfinity I was getting my iPhone 14 Pro the date that was expected. Once I received the phone,  I had to activate the phone and I was in the process of switching my primary number on my iPhone 13 to the 14. After looking in my account, I had a question if I was to switch phone numbers on the phones would this affect the promotion? I tried contacting the customer service line and no one called or contacted me on their "live chat." So the last resort was to go back to the Xfinity store to see if they can answer my question. They got me in and started to process my request on switching the numbers on the phones. After an hour and they are closing the store, they informed me I have to wait 7 days because they have to cancel my order for the previous order for the iPhone 13 and here's the kicker....they said if I were to switch the numbers, the promotion for the iPhone 14 Pro would be voided. I lost hope with Xfinity thinking they would accommodate my requests and needs but instead they cause me to waste numerous hours of waiting for a resolutions, weeks without a phone that I needed for day to day activities such as paying my bills and missing out on important calls, and stress with having to think Xfinity will charge me a phone that is ordered but I have not received. I never experience this in my years of being alive and I'm in the process of moving away from Xfinity with their internet and mobile services.

I've also want to input why do Xfinity have stores that doesn't do anything other than causing issues? The local Xfinity store is a joke and I would suggest closing that store down and save your business money.