Hindi 'jo' is che; 'jis-se / jis-ke' is cui
Hindi 'jo' is the plain link, exactly like 'che' — jo aadmi bol raha hai (la persona che parla). The 'jis-se / jis-ke / jis-mein' forms kick in after a postposition, exactly like 'cui' kicks in after a preposition — il motivo per cui. On complaints, note the cultural gap: Italy wants you polite but direct, so skip the Indian-English over-apology ('sorry to disturb you, maybe…') — a calm 'Vorrei fare un reclamo' is firmer and gets you served faster.
