There are three types of phones (here are connections) on the market. Contract phones, pay as you go phones and SIM free phones.
Contracted phones are those to which you receive a mobile phone and a selected network provider. These are like postal links where we assume that service fees are paid at the end of the contract period. The duration of the contract may be 12, 18, or 24 months. Until the term of the contract is completed, you will not be able to switch to another network. During the contract period, you can enjoy a number of engaging contract deals at affordable prices. So in simple words, if you buy a contract, you have to bind to a specific provider and services for the given contract period.
When talking about pay as you make a phone call, these are like prepaid connections where you have to pay in advance for any service provided by any of these providers. Contrary to contractual phones, if the credit amount is zero, you can not reach the requested service at any time. But while uploading your credit amount, you will have access to that service again. There is no need for a long contract period.
The last but not least SIM-free phones here when buying a device that does not come with a particular SIM card. This mode provides flexibility to select the selected SIM cards and can change them at any time. Similar SIM free phones are SIM deals only, which allows you to buy a SIM for your choice. Therefore, you do not need to buy a new device when you change your existing SIM.
The advantage of cheap SIM free phones is that it does not go into a long contract period. Additionally, you can change your existing SIM at any time when you find better services for other providers. Today, mobile subscribers prefer SIM free phones due to the above-mentioned advantages. Orange, O2, Vodafone, Virgin, Three and T-mobile are all eager to offer SIM free phones.