I’m Lizzy. A Guru on Shopify’s support team.
I'm sorry to hear you're having trouble with your account. Are you looking to set up Shopify Payments as a payment gateway to accept credit cards on your site? If so, you will need to connect a bank account to be able to receive the funds from sales. Shopify Payments is only available to businesses operating in certain countries, depending on where your business is located this may be why you're unable to complete the set up. This page here shows the Shopify Payments requirements.
If you're unable to use Shopify Payments this page lists the payment gateways we have available by country. You can set up any of the options listed for your country to take payments on your store.
If you're not trying to set up Shopify Payments, are you trying to attach a card to your account to pay your subscription costs? At this time Shopify is only able to accept credit cards as a method of payment for subscriptions. We can accept most major cards like Visa, Mastercard and American Express. Debit or credit-debit cards won't work with our system.
I hope this helps to answer your question. Please let me know if I can clarify anything further for you.