Secure Fiat Payment Gateway Integration

I'm seeking a secure and trusted payment gateway that allows users to pay with fiat (credit/debit cards) and enables us to receive that money quickly, similar to cryptocurrency (USDT).

Key Requirements:
- Support for Visa and MasterCard
- Must be easy to integrate as a plugin for Shopify or Wordpress
- Needs to be secure and reliable

Ideal Skills and Experience:
- Experience with payment gateways and Shopify integrations
- Familiarity with cryptocurrency transactions
- Strong expertise in security protocols for financial transactions

Please provide examples of previous work and ensure compliance with relevant financial regulations.