TalkTalk customers are being offered the chance to switch to the best-value deals previously offered only to new subscribers.
Anybody who has had a TalkTalk package for three or more months can change over and save money if the provider is offering a better deal.
The move has been taken after a study by the company revealed widespread frustration that market-leading deals are reserved for new customers.
Research revealed that many people feel loyalty is punished rather than rewarded and that more than four in ten British adults would like their broadband provider to change this above all else.
TalkTalk believes its pledge to offer the same best-value deal to both new and existing customers is a "groundbreaking move" for the industry.
This is one of several changes to come into force this week, as TalkTalk has also guaranteed not to increase broadband prices for 18 months and scrapped separate line rental charges across all its packages.
"Nothing matters more to us than our customers and doing right by them is the right thing for our business," said Tristia Harrison, Consumer Managing Director at TalkTalk.
"They’re frustrated with deals which shoot up mid contract and they hate seeing the best deals saved for new customers.
"We've listened hard to what they’ve told us and we’re acting on it."
TalkTalk's research also uncovered annoyance with increasingly promotional and celebrity-driven advertising in the broadband market.
Customers expressed frustration with "loud, eye-catching" ads that did not address how important telecoms services are to people's daily lives and failed to highlight "hidden catches".
TalkTalk has therefore pledged to make changes to its marketing approach, with forthcoming advertising focusing on a "real TalkTalk family".
Silly gimmicks and shouty ads (with catches hidden in small print) don’t do justice to how much this stuff matters to customers," Ms Harrison said.
"Especially now, with the country in such an uncertain place, people deserve security, peace of mind, to be talked to honestly."
Ms Harrison added that TalkTalk is determined to be a company that "makes things simple, tells the truth and most of all rewards loyalty".