I started with NYNEX Mobile then they merged and became Bell Atlantic NYNEX Mobile then they got bought out and became CelluraOne which was bought out by Verizon. However, I just switched to AT&T. Wow, I have had a cell phone for an awful longtime. lol.
I have sprint because of the unlimited data LTE coverage in my area no complaints over the last two years of using them and they're cheaper than AT&T and Verizon
I'm currently with T-Mobile, been with them since 2013ish. I've used them around the world without any issues. Before them I had Verizon for 2 years, Sprint for 2 years, and AT&T for a few years.
I've been with AT&T since I got my first iPhone. I thought I might switch to Verizon when I got my 6s, but after crunching numbers, we decided to stay with AT&T. And I'm happy with them.
Was with Cricket until yesterday. Left due to Voicemail delays and horrible customer service. Cricket's service is great for the money and never had any other problems. Ported over to Verizon's prepaid plan.