snippet.php

add_filter( 'booking_form_fields', 'handsomebeardedguy_booking_form_fields' );

function handsomebeardedguy_booking_form_fields( $fields ) {
	if ( isset( $fields['wc_bookings_field_resource'] ) ) {
		$pattern = '#\(\+*.*\)#';
		$replacement = '';
		foreach ( $fields['wc_bookings_field_resource']['options'] as $key => $value ) {
			$fields['wc_bookings_field_resource']['options'][ $key ] = preg_replace( $pattern, $replacement, $value );
		}
	}
	return $fields;
}