Locked phones can not be used on any mobile network besides the one through which it is purchased, meaning customers can not simply switch network providers while retaining the same handset.
Not all companies sold locked handsets, but enough of the big ones - such as BT and its EE mobile division, Vodafone, and Tesco Mobile - sold phones locked to their particular network. If a network can't lock you into using their service, it's much less appealing for them to give you the phone at a loss.
From December 2021 all United Kingdom mobile networks will be banned from selling locked phones in an effort to make it easier for buyers to switch networks at the end of their contracts.
"We know that lots of people can be put off from switching because their handset is locked", explained Selina Chadha, Ofcom's connectivity director. Furthermore, the new rules don't even come into force until December 2021. It also costs around £10 (around Rs 962) to unlock a network locked phone.
Another part of the code Ofcom is looking to implement is making switching broadband providers easier and more reliable.
The regulation will bring the United Kingdom place the United Kingdom in compliance with the European Union regulations under the European Electronic Communications Code that would be announced soon.
With Vodafone, it is free to request a network unlock code for most people - once a form has been completed and submitted, the company says it usually unlocks the device within 72 hours.
O2, Sky, Three and Virgin already sell unlocked handsets.
Facilitating switching between broadband providers - the guidance behind this rule is still being laid out, and it will not come into force until December 2022. And removing this barrier obviously makes it easier to shop around for a better deal, and increases competition.
Industry regulator Ofcom - which is responsible for the rule change - says nearly half of customers who try to unlock their device experience difficulties doing so, with more than a third of people put off attempting to switch.
"Also, our new rules include requirements that a switch is carried out in the shortest possible time and on the date agreed by the customer", Ofcom said.
The rules will come into effect from December 2021.
