The problem is that governments forcefully prevent competition and call that "natural monopoly." Personally, I would call that the opposite of a natural monopoly. The term is used very confusingly. Wikipedia gives one definition, which I think is reasonable, which is basically a (theoretical or real) environment in which a single producer maximizes efficiency. But the term used by governments and their supporters is something completely different, where the government forcefully prevents all producers but one from operating.
It's silly to talk about telcos "enjoying" a "natural" monopoly, when the airwaves are one of the most tightly-regulated industries, and in addition to being expensive for a competitor to enter the market, it's generally illegal.
The "natural monopoly" of telcos and other utilities comes from the limited amount of physical space available to run water pipes, electrical lines, and data lines. Not to mention the limited opportunity to install those services without causing disruption (typically when the land is first prepared)
It's not the case that everyone can simply spend the same amount of money as the first utility, and replicate it's services in order to compete.
It's silly to talk about telcos "enjoying" a "natural" monopoly, when the airwaves are one of the most tightly-regulated industries, and in addition to being expensive for a competitor to enter the market, it's generally illegal.