Ofsted regulate schools, but on the presumption you mean Ofcom, they haven't regulated that existing customers should be able to get new customer pricing. You're thinking of the Financial Conduct Authority, who have (unwisely) put in place such rules for car and home insurance, which will reduce switching, resulting in bigger market share and more market power for the largest companies. And if you've looked at your electricity bill lately, then the massive rise in the standing charge is precisely down to regulator Ofgem interfering in commercial pricing decisions, and now we're all paying for the companies who went out of business as a result.