Loyalty Broadband providers cost households hundreds of pounds in another year, according to a watchdog report.
Research of which consumer champion? Shows that most people have been with their broadband provider for at least three years and can be paying almost 90% more than a new customer.
On average these remain loyal to pay 15% more than people lured with cheap introductory deals.
TalkTalk has the most loyal customers of the 12 major vendors surveyed, with nearly 9 out of 10 remaining with the vendor for more than three years.
The average increase between the price of teletext introductory offer and the usual cost of broadband after the end of the transaction is 15%.
But the biggest increase in price is for the firm's fastest fiber speed Boost deal, which costs a 54% eye eye – from £ 25 per month to £ 38.50 – after 18 months contract period ends.
Alex Frieding, from the comparison site Broadbandchoices.co.uk, said: "It reinforces what we see over and over again – loyal customers pay a heavy price on their vendor confidence beyond their contract terms.
"Suppliers only clean up their actions if their customers start to vote with their feet denting their bottom line as there is currently a lot of money to be made from passive consumers."
Some people pay more
Eight out of 10 BT customers have also been stuck with the provider for at least three years, despite its average tariff being 23% higher than the average introduction to the deal.
BTs standard broadband package costs from 24.99 to £ 32.99 after 18 months – a 32% hike that costs £ 96 over a year.
The largest single increase was from the post office.
Its Unlimted broadband package leaped from £ 15.90, the cheapest introductory deal on the market, to £ 30 a month – an 89% increase of more than £ 169 a year.
Alex Neal, what? Director of Home Services, said: "Broadband customers will be furious to discover that their reward for loyalty is often a significant price hike without improving the quality of service they receive.
"Suppliers need to fight hard on your loyalty, do not take it for granted."
What vendors have to say to themselves
We are already giving notice before and after the contracts comes to an end as well as encouraging customers to sign up for another deal that provides a guarantee of no price in the middle of the broadband price contract.
"While recognizing that some customers enjoy the flexibility of being able to leave at any time, we reward loyalty by providing large transactions to those committed to staying with us."
A spokesman for BT said: "We fully agree that customers do not have to pay too much for the service they receive, and we believe that this is best achieved through clear communication with consumers about their options.We work harder than ever to be even clearer With our customers on their options, for example when new customers can benefit from promotional campaigns and we are very clear what the price will be when this period ends. "
A spokesman for the post office said: "We always look at how we can serve our customers in the best way, so we work with Opcom to feed their work around a broad industry approach to the announcement of contract termination, with the goal of ensuring these are useful to customers.
"We aim to provide a clear alternative from the main suppliers by offering the lowest unlimited UK broadband unlimited.We are clear to our signpost (outside contract) prices at the point of sale to ensure our customers can clearly see what they will pay during and after their contract before they do The transition. "