An electronic device sets an identifier for each contact stored in a phone book, automatically creates a short message which contains the identifier according to a preset message template, and sends the short message to a phone number of the contact to inform the contact of the identifier. In response to receiving a call from a contact, the device prompts the contact to input an identifier, and detects if one or more push-button signals have been received from the contact by a dual-tone multi-frequency (DTMF) decoder. If no push-button signal has been received, the device determines the contact fails validation. Otherwise, the DTMF decoder decodes the received one or more push-button signals to determine data information input by the contact, and then the device determines if the contact passes the validation by determining the data information matches an identifier of the contact that is stored in the phone book.