Ask anyone who was alive back then and they will tell you stories of how legendarily awful AT&T was to deal with. My father has told me several. The antitrust action made things better for regular people by allowing them to do things like buy their own handsets or haggle over price.
What telecom today will actually haggle
They won't haggle with consumers, but for large business customers the prices and other terms are absolutely negotiable.
All of them, in regions where they don't have a vertical monopoly. You can negotiate away installation fees and monthly package pricing on DSL, TV, internet phone... also sometimes get a no-contract deal instead of locking in for 24/28 mths with the dreaded ETF which is a large part of Comcast's profitability.