In the United States, most phone providers use phones that come with a contract or pay-as-you-go SIM card. In other parts of the world, things work a little differently.
Most of these buyers buy their phone directly from the manufacturers and get only the line and mobile network communications. These are mobile phones without SIM. However, the initial cost is the only area where a contract phone wins. Many phone providers will try to give the notion that their phones are free with the contract. However, the phone is not free at all. You pay for the phone over the life of your contract and any usage not included in your package.
Even if it is not free, it is considerably lower than that of the SIM-free mobile phone version. Most phones are locked to the networks you buy them on. This means that you can only use the phone of the carrier that has applied the lock. All in all, SIM-free mobile phones are the best options.
If you want to use the SIM card of other carriers, you need to get the restriction code first. The way to obtain the restriction code differs depending on the cell phone provider.
Some providers will give you the restriction code for free or after a certain number of months in your contract. Some may even ask for a fee while you’re still under the contract period, but may give it to you for free thereafter. And some cell phone providers will outright refuse to give you the restriction code. So you have the mobile without SIM; that can be used with any provider.