It's the governments, generally, who grant them the monopoly in the first place.

Though if you look at the history of anti-trust and telcos in the US, it was the anti-competitive practices of AT&T (as early as 1917), which resulted in anti-trust actions being taken against them. At the time it was setting inter-connect fees to other carriers sufficiently high that the competitors were forced out of the market.

Now, why does this suddenly remind me of various "carriage fees" proposed by contemporary broadband providers....