Methods and systems for top-up are provided. A representative top-up system includes an interface module that receives and transmits a phone number associated with a phone user's account; and a top-up gateway that receives and transmits the phone number from the interface module and requests for a telephone service company associated with the phone number to a home location register (HLR) look up service. The top-up gateway tops up phone minutes and/or balance of money of the phone user's account associated with the phone number based on the phone number, and requested telephone service company.