You cannot use Globe billing method on IOS, because Purchasing in IOS can only be made with Credit/ Debit Card or Paypal. Or you can use G-Cash instead of Globe billing. SMART and GLOBE Billing only apply in ANDROID or GOOGLE PLAYSTORE users.
I recommend if you have an extra android phone to purchase on that phone. Im also an IOS user but im using Android phones for In-App purchasing.
HOPE THIS COULD HELP