As anyone who's found themselves stuck in an expensive mobile phone contract can probably tell you, the lack of freedom and consumer power available in such fixed-term plans can be very frustrating. A less restrictive alternative is a SIM only plan, which gives consumers more freedom of choice and greater control over how much they spend.

To begin, SIM only plans differ from contract-based mobile plans in that they are prepaid, flat-rate plans which are not dependent on the particular make or model of mobile phone they're paired with. SIM only mobile plans are presented as packages of calling, texting and Internet credit that customers can purchase according to the amount they can afford and the amount they plan to use.

One of the main benefits of SIM only plans is that they do not require users to sign a contract, giving them more control over how much they spend as well as the freedom to switch service providers whenever they like. Consumers who find themselves faced with an extensive 2-year contract are often intimidated by the financial commitment, and rightly so. Such plans can include hidden fees and may bind you to a service provider you're not happy with.

Another benefit of SIM only plans is that they do not require consumers to purchase a particular type of mobile phone. By choosing a SIM only plan, consumers can choose to use their existing mobile phone or, if desired, can purchase a new model. Since the mobile plan is based on SIM credit, not the device itself, consumers can change devices as often as they wish. For anyone who's held onto an old, worn-out mobile while waiting for their contract to cover an upgrade, the SIM only plan may be a less maddening option.

Finally, SIM only plans often appeal to consumers who make a lot of international calls. Here in Australia, for example, a growing number of expatriates are choosing prepaid SIM only plans that offer high-quality international calling at flat, national rates. Since many contract-based mobile plans charge extra for international calling, a SIM only plan is often a far less expensive option.