WHMCS Default country and payment gateway

Hello I have a project regarding the payment form on WHMCS. I need to pass the country code through a POST or GET request in the URL, and the form should display that country as the default selected option. Additionally, I need the payment methods to change based on the selected country. For example, if I choose 'US', the form should set the default country to the USA and show payment methods like Stripe and bank transfer. However, if 'ES' is selected, the form should hide the bank transfer option and display only Stripe as a payment method.