my phone cannot be charge for billing

Greetings BoonHeng,

Thanks for visiting the Apple Support Communities! It seems you're unable to make a purchase with mobile phone billing as your Apple ID payment method.

The following support article outlines the areas where mobile phone billing is an available payment method, the carriers who support mobile phone billing, and how to set mobile phone billing as your Apple ID payment method: Set up mobile phone billing as your Apple ID payment method

If you're unable to complete a purchase while using mobile phone billing as your Apple ID payment method, then I suggest following the "If you can't make purchases with your mobile phone billing" section of the provided guide: "If you have questions about billing limits or if you get a message that your transaction declined, contact your carrier. If your concern is related to purchased content, contact Apple."

If further assistance is needed, it would be helpful to know more details on the behavior you experience while attempting to make a purchase with mobile phone billing as your Apple ID payment method.

Kind regards.