Canada

What if there's no competing companies, but a monopoly (as is the dream of capitalists) or a cartel (a lesser dream)?

Let's not forget that these companies aren't really running on profits from customers. They're running on venture capital bro driven development. Uber lost money for 15 years.

You understand the idea of a free market. Now, do crony capitalism, which is the present reality.

Capitalism works great in theory, but in practice "market forces" are undermined by monopolies, collusion, and regulatory capture. ISPs are a good example, in many places they collaborate to ensure their coverage areas don't overlap so that they can all charge as much as possible.

Provided someone is willing to provide such a fair and effective competing service, and doesn't go out of business due to much lower profit.

Market forces are not capitalism, they're a component that is utilized under certain conditions in capitalism, and not only in capitalism. Most markets trend towards oligopoloes and monopolies. It's now easy to see how. Competition literally leads to consolidation. The market share of failed competitors, often their equipment and other assets, and even often their former employees become part of the winning competitors' operations. Rinse and repeat till you end up with very few, very big players.

You can't say things like that about communism. Straight to the gulag.