I want to update my account payment

According to Apple:

• If you can't add a payment method, make sure that the payment method is accepted in your country or region.
• Learn how to change your payment method.

Need more help?

• Chat now or call 1-800-APLCARE.
• International Support.

You can update your payment method here:

Settings → Apple ID → Media & Purchases → View Account → Manage Payment Methods

You must add a new card before the old card can be deleted if you have an ongoing subscription.

You can find more useful information here:

Add a payment method to your Apple ID - Apple Support