For those who don't need a new mobile phone or want a short-term minimal-obligation mobile plan, a SIM-only deal might be the best idea. All the major networks let you sign up to 30-day contracts with a Pay Monthly SIM, and on these contracts you can get some great allowances at much lower costs than if you were to buy a new phone at the same time. If you decide to end the contract, you only need to give 30 days' notice and then it's done. This option is very popular for people who have reached the end of their old contract but don't want a new phone. By getting a Pay Monthly SIM they can get a great allowance at a much lower price than their old contract. To transfer an old phone over to a new network you will need to call your old network provider and ask for the unlocking code and PACPAC code for your phone (the PAC code will let you keep your old mobile number on your new SIM card). Transferring an old phone onto a new SIM is very easy and takes no time at all, and before long you will be up and running with a phone that you love and a contract that couldn't be better.