What you describe in Nigeria sounds like crony capitalism. The Government and the private monopolies are working together to get rich at the expense of the public. In western countries it is more difficult for them to get away with that. Therefore, we have oligopolies instead. They create the impression of competition but there is very little. In many ways they are just like monopolies.

Government monopolies can provide very low price services. They could even provide free services but that does not make them efficient or good. The taxpayers are paying for all of the Governments inefficiency and even corruption through higher taxes.