Circa 2004, my last words to Sprint after 3 weeks of back and forth trying to get my phone working again: "Close my fucking account." I also switched to T-Mobile. Called them up immediately afterwards, spoke to a rep in the US (or at least spoke clear English with no cross-ocean lag) and had a phone overnighted to me the next day. Painless.
Background on it: I'd upgraded my phone w/ Sprint. And not long after receiving the new phone, it fell out of my pocket and landed in the toilet. Dead dead. No amount of rice was going to save it. This wasn't Sprints fault, never said it was to them. But, I still had my previous phone, so I call up, explain what happened and asked them to reactivate my old phone. And they did, great so far. The old phone worked fine for a month or so until it just didn't work anymore. I could still contact them using the phone via whatever their "*" number was, but I couldn't make any regular calls. I spent upwards of 40 hours over 3 weeks trying to get it resolved before I'd had enough.
The final call started with a recap of the issues and lack of progress and me stating that if the issue wasn't resolved tonight, I was closing my account. After another 2 hours on the phone, they gave up and told me "the only person that knows how to do this has gone home for the night". So I told call the rep to call them. They wouldn't. Lost customer. Switched to T-Mobile and haven't looked back. It's been nearly 20 years, still with T-Mobile. I've not had any issues like that, and every time I have had an issue, support has been great. I was dreading the Sprint acquisition, fearing support would tank. Thankfully, I think I've been wrong on that fear.