pay-as-you-go
adjective [ before noun ] uk/ˌpeɪ.əz.jəˈɡəʊ/ us/ˌpeɪ.əz.jəˈɡoʊ/
预付费的
A pay-as-you-go system is one in which you pay for a service before you use it and you cannot use more than you have paid for.
a pay-as-you-go mobile phone 预付费手机