With pay as you go you only order a sim card which you can topup, so you can keep calling with your current mobile phone. In contrast to sim only contracts with PAYG you won't be charged any monthly fees. You only pay upfront, as you go, and can top up whenever you wish to do so. Using a PAYG sim card you are completely free, and always on top of your mobile costs. For your convenience we already selected the best Pay As You Go deals.