A SIM-only plan is a mobile phone service that provides just the SIM card without a new phone. This means you can keep your existing device and simply switch the SIM card to access mobile services like calls, texts, and data. These plans are often more affordable than traditional contracts because you’re not paying for a new phone. These plans typically come with flexible contract lengths, ranging from one month to a year. They are ideal for people who want to save money or those who prefer to upgrade their phones independently. With a SIM-only plan, you can choose the data allowance that suits your needs.