Start with the transaction direction
Buying and selling reverse the flow of funds and use different pricing events. A Buy starts with a bank amount in EUR or USD and an estimated native-USDC output. A Sell starts with an exact native Ethereum USDC amount and a bank payout quote that has an expiry.
Read the dedicated direction guide first. Then use the fee, network, eligibility, security, and help resources to resolve the details that apply to the customer and current order.