As far as I know, the question typically doesn't turn on whether a company is/has "a monopoly". Rather, what's restricted is the exercise of monopoly power. In

As far as I know, the question typically doesn't turn on whether a company is/has "a monopoly". Rather, what's restricted is the exercise of monopoly power. In a nutshell this means altering market prices or availability in a way that would not be possible if the market were genuinely competitive (because some competitor would come in and close the gap your change created).