I was a Verizon Wireless subscriber for about two years while living in Southern California / Orange County. At the time I switched from T-Mobile, mostly due in-part to the fact that when I switched, the coverage for T-Mobile in SoCal was absolutely abysmal. While you would technically have a connection to a tower on a regular basis, it was very often the case that the data rate would be completely unsustainable.
They had a billing and general website that barely worked. I routinely experienced cryptic error messages on the website, doing such things as trying to change the billing information on my account, login, or change SIM cards. I remember experiencing issues with the payment system essentially on a monthly basis, including them not applying AutoPay discounts. Customer support would be apologetic, but this did not improve when I used them. My company paid for a portion of my costs, so I was on the highest/best plan/tier, but subsequently downloading the bill and uploading it to my company's expenses system was a 10 minute job each month.
Moving phones on Verizon is an exercise in frustration quite often. I moved phones with and without doing the eSIM transition, and it was always painful. Particularly on iPhone launch day, the transfer process would just not complete or leave me in an unhappy state. Once again, the only option was to contact customer service, who would be apologetic and eventually move the line to the new phone. However, waiting on hold or on live chat always took 15-30 minutes for this service.
For once in my life, I tried to get some of the rebates that Verizon and Apple cross-promoted at the time. These would be like a $300 gift card for Verizon if you activated a new Apple Watch purchased at Apple on their network. I did three of these promotions, and of them, only one of them worked correctly. The other two were more painful. One was successful and one wasn't. Though I met the promotion terms, I had trouble getting the gift cards to be issued. I contacted Verizon's support, and the staff were more than unhelpful, saying that they only knew about worse promotions, or that they didn't have any at all that I qualified for. According to the terms on Apple's website, I qualified, but Verizon employees were incapable of visiting the Apple website to look for themselves. They didn't listen to me when I read the terms directly to them, insisting it wasn't in their system.
For the gift cards that were eventually issued under this promo, I couldn't apply them to my Verizon account as payment, because the aforementioned website issues would routinely lead to errors applying the gift card balance.
Eventually I ended up buying AirPods from the Verizon online store and re-selling them because of how terrible the gift card bill-payment system was.
When I ultimately cancelled my account, I had to wait on hold for about an hour to get a representative to talk to.
The cancellation representative assured me that the gift cards (which were, at the time, unspent) would just be cancelled and I wouldn't pay any additional charges. Instead, Verizon charged me the full value of the gift cards and refused to just cancel the gift cards.
Until I moved out of the United States, I was getting 8-10 flyers from Verizon in the mail per year, asking me to come back and dangling various benefits in front of me to get me to move, including more Verizon gift cards (the cap out on the offer was a $600 gift card just to create an account again) and various free iPhones. These offers were genuinely really good – at least one of the iPhone offers didn't even have a contract or claw back terms on it, but I was so irritated by Verizon spamming me (and the irony of offering gift cards on a routine basis) that it just completely killed any chances of me going back.
Verizon did have decent service in my area. The times I did get to use their UWB network were really fun, but it was so infrequent that I didn't think it was worth keeping. I switched back to T-Mobile, which ended up being nothing short of a great carrier in terms of both customer service and actual service for the remainder of my time in the US.