I’m trying to update my payment method and it keeps saying iTunes Store is unable to process purchase at this time

If following the steps provided by this support guide doesn't help you:

Change or remove your Apple ID payment information - Apple Support

contact iTunes Store Support and explain your problem, filling out and sending this form:

iTunes Store - Contact Us - Apple Support

Regards

Giulio

I am trying to change the credit card information for my payment method and it is returning an error code saying unable.