A prepay mobile phone (also commonly referred to as pay-as-you-go, pay-as-you-talk, pay and go, go-phone or prepaid) is a mobile phone for which credit is purchased in advance of service use. The purchased credit is used to pay for mobile phone services at the point the service is accessed or consumed. If there is no available credit, then access to the requested service is denied by the mobile phone network. Users are able to top up their credit at any time using a variety of payment mechanisms.