There are three kinds of phone (here connection) available in the market viz. Contract phones, pay as you go phones and SIM free phones.
The contract phones are those where you get a handset along with a particular network provider of your choice. These are like postpaid connections where you are suppose to pay your service charges at the end of contract period. The contract period can be of 12or 18 or 24 months. Until that contract period is completed you can not switch to any other network. You can enjoy several sizzling contract deals within the contract period at affordable rates. So in simple words, if you buy a contract phone you are bound to a particular service provider and its services for the particular contract period.
If we talk about the pay as you go phones, these are like prepaid connections where you have to pay in advance for using any service of the particular service providers. Unlike contract phones, if your credit amount is zero at any time you can not access the requested service further. But as you top up your credit amount you can again access the particular service. Here you do not need to enter into a long contract period.
The last but not the least is SIM free phones, here when you buy a handset that does not accompany with a particular SIM. This mode gives you flexibility to choose a SIM of your choice and whenever you feel to change it, you can do that easily. Alike SIM free phones there are SIM only deals that gives you freedom to buy a SIM of your choice. So you do not need to buy a new handset whenever you change your existing SIM.
The benefit of cheap SIM free phones is that you do not enter into a long contract period. Moreover, you can switch your existing SIM at any time when you find some better services by other service providers. Nowadays, mobile subscribers are more preferring SIM free phones due to the aforementioned benefits. Orange, O2, Vodafone, Virgin, Three and T-mobile, all are offering tempting deals on SIM free phones.