I bought a t-mobile phone and had terrible trouble putting more money into it. Hours of my life I will never get back. I had just arrived and bought the phone. I had no idea that calls into the phone would cost me (not so in Australia) - so calls in from home checking that I had arrived safely depleted the funding at a rapacious rate. I spent fruitless hours trying to add more money. The helpline people kept pointing me to a phone number which was all automated. That line insisted on my 5-digit postcode as associated with my credit card. We only have four digit postcodes in Australia, and there was no way around that - I even tried adding a leading 0. Despite this, my credit card was readily accepted everywhere else in the States. When I tried to explain this to the help-people, I got nowhere - they pointed to online. I found a terminal. Online adding money did no better (no need for details), so I rang them back yet again. Maybe I was messing up somehow, but I just couldn’t get any help other than guys following some standard script who then gave up on me and my four-digit postcode. In the end I had to find other ways around having no phone in an emergency and then get a refill card the next day.
Given the phone was sold at the airport specifically for travelers who don’t want to use the ridiculous roaming charges from home, this scenario has convinced me to just get a US sim-card next time. But that means my usual phone number goes out of action.
Off topic: whenever I got into confusion or messes traveling in the US over the 4 week trip to all sorts of strange places, there was ALWAYS some stranger who came to my aid, often to an unbelievable degree. Can’t speak highly enough of American friendliness to an Aussie traveler. Except for T-mobile.