That meant that they could decide which services and features you had, and could ask the government to intervene to block competitors who added services and features they didn't like. They wielded this power without restraint or mercy, targeting, for example, the #HushAPhone, a cup you stuck to your phone receiver to muffle your speech and prevent eavesdropping:
https://en.wikipedia.org/wiki/Hush-A-Phone
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They didn't block new features for shits and giggles, though - the method to this madness was #RentExtraction. The iron-clad rule of the Bell System was that anything that improved on the basic service had to have a price-tag attached. Every phone "feature" was a recurring source of monthly revenue for the phone company - even the phone itself, which you couldn't buy, and had to rent, month after month, year after year, until you'd paid for it hundreds of times over.
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