Is 100% Market Share Monopoly Anti Competitive?

When I lived in Boston, I had the choice of exactly one company to get my phone and internet from. And it was Comcast. It was a big deal when Verizon FiOS came in and started competing with them. So if you have a situation like that where I am just a captured customer, like I live on the internet, I cannot do my job without it. That's where it becomes a problem. To be clear, 100% is a monopoly. But where we have zero choices as customers, let's start there.