Martin Lewis shared a “massive” warning with some 14 million people this week, during an appearance on This Morning. The Money Saving Expert founder was live on the ITV daytime show via video link, when he said many people who are out of their mobile phone contracts are paying “four times more than they need to”.

He went on to explain that “existing customer deals have gone up and up and up, but yet at the same time the cheapest deals have got cheaper and cheaper and cheaper.” He urged everybody watching at home to pick up their phones and text the word “INFO” to 85075.

Martin added: “You should get a reply back and the reply will tell you, what you’re looking for is what your early termination or cancellation fees are. It’ll tell you effectively if you’re out of contract and free to switch.”

If you’re with Three, iD mobile, or Smarty, you may also be asked for your date of birth. Mr Lewis also said that those on a family contract won’t be able to check in this way either and said if this applies to you “if you haven’t done anything for 18 months, two years, you probably are [out of contract]”.

He said that people could easily save hundreds of pounds by switching to another contract or provider.