Make it sure that you have ZERO load balance. Just balance inquiry to be sure.
If Globe's reply is " Insufficient balance " , that is good. Go ahead and reload 15 php and proceed with the trick.
If the reply was " IncorrectKeyword " or something similar, I'm afraid the subscription can't be done on your area or Sim Card. You can try purchasing another Globe sim though.
Send GOTXT15 to 8888 and wait for the confirmation.
Send GOTXTMB15STATUS to8888 and wait for the confirmation.
You will receive the confirmation status and you will see there that you have 31 GB worth of mobile Internet data and you may now Enjoy surfing for 3 days!