United Kingdom telecoms regulator Ofcom says many people end up staying with providers because of the hurdles of trying to switch.
Vodafone, which has been slammed by Ofcom for poor customer service, saw its share price fall from 232.6p just after the markets opened to 231.3 by midday.
One of the major problems was the need to speak directly to a current network provider in order to make the change.
But the new rules won't be in place until June 2019 to give providers enough time to get ready for the changes.
It says that one of the biggest hurdles in the process is phoning your network to request a porting authorisation code (PAC), the code you need to give to your new phone provider so you can keep your number.
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"For more than a decade Three has been encouraging Ofcom to do more to ensure that consumers can easily switch mobile phone provider and get the best deal", said a Three spokesperson.
"Our own research from earlier this year found that while one in five thought text-to-switch would make them more likely to switch provider, more than double would have been encouraged to change under a gaining-provider led process, the alternative system that Ofcom decided against". Companies desperately want to keep you, so if they believe they will lose you, you can often get much better deals. The user can then send the code on to their new chosen service provider, who will set them up within one working day, with no notice period charges or other fees to pay.
This will put an end to people paying for old and new services at the same time, with the regulator claiming to be able to save consumers £10million a year.
From 1 July 2019, mobile users will be able to request a switching code by texting a free number, by going online or by calling their provider.
The new provider will facilitate the switch within one working day, with the old service ending on the same day.