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Mobile phone customers can now switch providers with a single free text under new rules which have come into effect.

At the moment, customers have to phone their mobile provider when they want to switch to a new firm.

They are then given a porting authorisation code (PAC) to give to a new provider if they want to keep the same phone number.

But watchdog Ofcom says the need to speak to a provider can be one of the main factors stopping people switching.

As part of this process, customers can often find themselves dealing with unwanted attempts by the companies to persuade them to stay.

How to switch by text

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Customers who want to switch and keep their existing phone number text "PAC" to 65075 to begin the process Their existing provider will respond by text within a minute They will then be sent their switching code (PAC), which will be valid for 30 days The provider's reply must also include important information about any early termination charges or pay-as-you-go credit balances The customer then gives the code to their new provider, and this company must arrange for the switch to complete within one working day While most people want to keep their mobile number when they switch, about one in six do not. These customers can text "STAC" to 75075 to request a "service termination authorisation code".

Ofcom says the new text-to-switch process will make it quicker and easier for people to leave their mobile company.

It will also give them control over how much contact they have with the firm.

After sending a single free text, customers should be switched within one working day. However, there may be early termination fees if you leave before the notice period of your existing contract.

Lindsey Fussell, Ofcom's consumer group director, told the BBC that the changes were designed to deal with the issues that put people off switching mobile phone providers.

These included the need to pay for both the old and the new service at the same time during an overlap period.

"It really has never been simpler to switch," she said.

If mobile phone providers did not abide by the new rules, they would be subject to investigations and even fines, Ms Fussell added.

In November last year, Ofcom fined Virgin and EE £13.3m for leaving customers who quit broadband and phone contracts early "out of pocket".

"We won't hesitate to do the same again if we need to," said Ms Fussell.