If you don’t intend to use your cell phone much, Walmart carries the Tracphone. You buy it and then pay for a $30 a month card that covers limited use and texting, or $45 for unlimited. I got this for my teenager and told him he was on his own for paying for the $45. It worked great. But this wasn’t a smart phone.
I got a smartphone (an iPhone) last year, given to me by my then boss. I am in love. It has completely changed the quality of my life.
In answer to your question, the major carriers share big towers. However, nationally Verizon has the best coverage. ATT is widely hated for poor coverage and quality. I do business with Verizon and have never had a single billing problem for my home phone, Internet, cell, or business billing at the office I was running until recently. Others hate them but I don’t know why. They’ve been great and their (Indian) customer service for Internet is fantastic.
Thank you.