What should I do if my customer sent a different currency from the one I requested?

Ask for the bank receipt and confirm the currency actually sent, not just the currency on your invoice. Also check which receiving account and transfer method the customer used.

Send Support the receipt, your invoice and the intended receiving instructions. Explain whether the payer converted the amount before sending or selected the wrong currency. Support needs to check the actual account and payment; do not assume any account can receive and convert any currency.

Keep the original invoice and transfer record unchanged. Do not ask the customer to send a second payment or an extra amount until the first transfer's handling is clear. Agree the correct sending currency in writing before any future payment.