Net10 phone says "dial 438 from add airtime option to add reserve"?

Hi. My friend has a Net10 phone and selected the 750 minutes/30 days monthly plan. He entereda the pin from his card, and the message “dial 438 from add airtime option to add reserve” came up. According to Net10’s website, the monthly airtime stays on reserve until service days are up. He has 6 service days but no minutes. Net10 said to put 438 in the airtime menu. He tried this and said nothing comes up. I also checked on the account online, and it said there is nothing in reserve. I am confused. I can’t mess with the phone myself because I am in another state. Any suggestions would be appreciated – I never used airtime on reserve before.