im buying in-game purchase but it says it’s not completed and referring to apple support

Hello ~ Go ahead and contact Apple for assistance as this can have lots of causes. You may also click on the following link and choose your country for assistance…

Choose your country or region - Official Apple Support

Also…

Contact Apple for support and service

~Katana-San~

it’s keep saying purchase incomplete

If you get a message -> Your purchase could not be completed, you need to update your payment method or add a new one. 

See also the following Apple articles:

Payment methods you can use with your Apple ID

Payment methods you can use with your Apple ID – Apple Support (UK)

Add money to your Apple ID balance

Add money to your Apple Account balance – Apple Support (UK)

• If you want to change your card, add first the new card, then remove the old one.
• or if you use your Apple ID balance, set your Apple ID balance as your default payment.

If you update your payment method or add funds to your Apple ID balance, It would take about 1 to 3 business days in order to process.

If you're still unable to update your payment method, Contact Apple Support.

Click here for more support and assistance.