Check out Straight talk. It's from Walmart and it is cheap. I pay $45/month for unlimited. You do have to pay upfront for a phone but can buy one anywhere and bring it in. It may have to be a certain kind of phone or meet some requirement; I don't know. I have an iPhone 6 that was a refurbished model several years ago that I got for Christmas. Before that I had an old, used iPhone 4 and before that a phone I bought through StraightTalk that was a cheap Smart phone.

It's a lot better than what I've seen with other phone providers and the service is fine. Mine uses Verizon towers which are the only ones that work here but I think they change it out wherever you live.