Firms will also have to inform customers every year about the best alternative deals on offer, the regulator Ofcom said.

More than 20 million customers stay with their provider after the initial tie-in period comes to an end, Ofcom research found.

Many of these people are paying over the odds.

Those who bundle their landline and broadband services together pay, on average, around 20% more when they are ‘out of contract’. This rises to 26% among customers who bundle their pay TV with these two services.

What exactly will providers have to tell you?

Under the new rules, telecoms and pay TV companies must alert customers between 10 and 40 days before their contract comes to an end by text, email or letter.

The alert must include:

• the contract end date;
• the price paid before this date;
• any changes to the service and price paid at the end of this period;
• information about any notice period required to terminate the contract; and
• the best deals offered by their provider, including telling loyal customers what prices are available to new customers.

People who choose to stay with their provider without signing up to a new contract will be sent a reminder every year about their firm’s best deals.

Lindsey Fussell, consumer group director at Ofcom, said: “We’re making sure customers are treated fairly, by making companies give them the information they need, when they need it.

“This will put power in the hands of millions of people who’re paying more than necessary when they’re no longer tied to a contract.”

Companies have nine months to make the necessary changes to their systems and processes and customers should start receiving notifications from 15 February 2020.

Switch and save hundreds

Natalie Hitchins, head of home products and services at consumer group Which?, said: “Until now many customers have found themselves paying over the odds for staying with their provider after their initial contract has ended – so notifying people in advance that they may be about to be hit by these poor value rolling tariffs is a step in the right direction.

“Providers should be fighting hard to show that they deserve to hold on to their customers, not hitting them with an unexpected price hike the minute their contract is up.

“Anyone nearing the end of a contract should compare prices to see if there is a better deal available – switching suppliers could potentially save you hundreds of pounds a year.”