Ofcom has criticised broadband providers for deliberately downgrading their service levels.
Openreach's wholesale customers have the option of paying extra to get faults on a line repaired inside one working day or to take up the standard two-day option.
According to Ofcom, Sky and TalkTalk had paid for the premium repair service early last year, but later changed to the cheaper alternative.
Speaking to the Financial Times, a TalkTalk spokesperson insisted it was not downgrading its service in an effort to save money.
Indeed, the official said the company has actually invested in improving its own diagnostics, so it would not have to use Openreach engineers as frequently.
"When something goes wrong, we know our customers think it is more important that we just work out what the problem is quickly and the engineer can fix it in one appointment," the company stated.
Sharon White, Chief Executive of Ofcom, added that broadband providers in the UK must do more to improve their customer service, as some major providers are rated lower than banks.
"The fact that the telecoms industry is so far behind should be a concern for us all,” she commented.
According to Ofcom's latest figures, BT, Plusnet and TalkTalk were the most complained about broadband providers during the fourth quarter of 2016.
BT was the subject of 33 complaints per 100,000 subscribers between October and December.
Plusnet was not far behind, with 30 complaints per 100,000 subscribers, while TalkTalk racked up 29 complaints per 100,000 subscribers.
EE also fared badly in the data, with a figure of 26 complaints for every 100,000 customers.
However, some major broadband providers did perform relatively strongly throughout the quarter.
Virgin Media was the subject of just 13 complaints per 100,000 subscribers, while the figure for Sky was eight complaints per 100,000 customers.