Purchasing a cell phone from a particular mobile phone service provider means that the device is configure or locked to use only that service providers subscriber identity module that only gives access to that service provider. An unlocked cell phone however is one that is not configured or programmed to a particular service providers and one has the advantage of using a service provider of their choice, this helps to answer what is an unlocked cell phone. One is able to switch and use different service providers without the need of buying new devices, it also gives the user control over the option of provider and one can enjoy services from any provider without having to get into lengthy contracts that may tie them down, the hustle of not getting services while out of town is eliminated with the presence of prepaid SIM cards that one can move around with and continue enjoying their services and avoid providers with high cost services.
Some may argue that purchasing an unlocked phone is expensive but companies that sell locked phones at subsidized prices spread their charges on phone bills for the duration of the contract thereby ending up being more expensive that buying an unlocked phone sold at retail price.