Broadband, television and telephone customers will be able to avoid large price increases when their contracts expire under rules taking effect on Saturday.
British watchdog Ofcom says users could save £ 150 a year on broadband only once they know about alternative offers.
About 20 million customers are in breach of contract with their suppliers, which leaves many paying more than necessary.
The regulator says people can earn big monthly savings if they know about discounts on new offers in advance.
Matt Powell, editor-in-chief of the Broadband Genie comparison site, said that requiring companies to notify of expiring contracts would help loyal customers stay on top.
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"Many broadband offers are sold with discounts for the initial term of the contract, and although these are often good value for the first 12 or 18 months, the cost after the discount ends can be considerably higher ", did he declare.
"A regular change will allow you to take advantage of the latest offers and perhaps get a faster connection. And if you don't want to change, you should always negotiate with the supplier at the end of your contract period to see if a better deal is available. "
Some 25,000 broadband customers are contracted daily, which generally leads to automatic price increases.
Ofcom says the new rules, which take effect on February 15, could help consumers save £ 150 or more on their annual bills.
Service providers must send SMS, send e-mails or write to their customers between 10 and 40 days before the end of their contract, specifying:
- the date their contract can be terminated without penalty
- the price they paid
- any change in price or service that takes effect automatically after this date
- how much notice they must give to cancel the agreement
- the best alternative subscriptions offered, including prices charged to new customers