I agree with Max, I thought Verizon was OK and paying $110./mo. for 4 gigs data until a T-Mobile lady (right next door to Verizon in the mall) seduced me into switching over. They paid off my $500. LG phone from Verizon, paid off the rest of the 2 yr. contract and gave me an 8 inch Alacatel tablet free. Now I pay $60./mo. unlimited everything, no contract and get Netflix free- I ain't never lookin' back. But it makes me think how lucrative that business must be...
I am not > 55, so not eligible for the $60/mo (now $70/mo for new customers). But they twice let me change plans to something better, the last time being something they don't advertise.... unlimited everything except data is 6GB per line (which is at least three to four times what I would ever need or have ever used, then it just throttles after that), TWO LINES, no Netflix, $80.24/mo!!
When I bought a new Moto G5+ phone on Amazon, I discovered the SIM didn't fit.... there are no activation fees on T-Mobile (unlike most carriers), but still needed a new SIM card. Walked into a T-Mobile store and they replaced it with the newer smaller one FOR FREE, and in just 2 minutes, and were super-friendly and helpful (like every interaction I have had with them, online, on the phone, or in a store, over the last 4+ years).
Few weeks later, did the same thing for Mom when I went to visit her in another city. Exact same experience.
At work we still use Sprint... had to activate a new pre-purchased phone on their network (get a SIM card AND programming, since they don't really tie the SIM to the service). Had to wait 20 minutes for help, then it took them 20 minutes just for them to figure it out, AND they charged us $25. I left Sprint for home use after being a customer for 16 years- I couldn't stand the horrible technology problems, billing problems, and generally poor customer service anymore. Best decision EVER.
Now this thing with T-Mobile trying to merge with (more like buy) Sprint, it makes me nervous. If it actually happens, I hope they don't change or inherit any bad Sprint behaviors and problems. Trying to keep an open mind...