Telecoms watchdog Ofcom is proposing a ban on the sale of locked handsets, to make it easier for consumers to switch between mobile phone networks.
It says BT/EE, Tesco Mobile and Vodafone are among providers that sell mobiles that cannot be used with alternative operators without being "unlocked".
This requires a code provided by the original network.
And Ofcom says "nearly half" of customers find the process difficult.
Some operators charge for the service. Tesco, for example, charges £10 to unlock a pay-as-you-go handset that is less than a year old.
O2, Sky, Three and Virgin do not restrict customers to locked devices.
"By freeing mobile users from locked handsets, our plans would save people time, effort and money - and help them unlock a better deal," Ofcom consumer group director Lindsey Fussell said.
Ofcom is now running a consultation on the proposals.
Three said it welcomed the plan and "urged" Ofcom to introduce it as soon as possible.
The watchdog also wants to make switching broadband provider easier, in line with new EU regulations.
Last week consumer group Which? said customers could save £120 a year by making a change.