sv-wc-bambora-set-currency-merchant-id.php

<?php

/**
 * Sets a unique Merchant ID depending on the order currency for Bambora transaction requests.
 *
 * @param array $request_data transaction request data
 * @param \WC_Order $order order object
 * @return array
 */
function sv_wc_bambora_set_currency_merchant_id( $request_data, $order ) {

	$wc_version = defined( 'WC_VERSION' ) && WC_VERSION ? WC_VERSION : null;

	$currency = ( $wc_version && version_compare( $wc_version, '3.0', '>=' ) ) ? $order->get_currency() : $order->get_order_currency();

	switch ( $currency ) {

		case 'CAD':
			$request_data['merchant_id'] = 'CAD_Merchant_ID'; // Your CAD merchant ID here
		break;

		// repeat ^ for any other currencies that need their own Merchant ID
	}

	return $request_data;
}
add_filter( 'wc_beanstream_credit_card_legacy_request_data', 'sv_wc_bambora_set_currency_merchant_id', 10, 2 );