I see it like this: If you talk to a telecom company, I'm sure they will tell you they believe they are giving you the service quality you're paying for. Many of them will say that to you if you talk to them. However, in my opinion, if there's nothing wrong with their average network performance according to the telecom company, they have nothing to fear from a bill that makes that network performance data transparent and publicly available.
Customers win in either case or direction. They get good-quality service and empowering information, or, in the other direction—if it turns out it's true that people are not getting what they pay for, customers win in that scenario as well. They get more information about what they're paying for and there's more onus on the telecom companies to deliver the services they're advertising.