Hello, faulty video projector bought a few days ag...

Hello, faulty video projector bought a few days ago. The technical department of the store tells me that it works well, without testing it in front of me. Refusal to exchange it, refusal of a voucher and no other explanation apart from telling me to contact the claims department. It's been 3 days that a Sav manager has had to call me back; i think can still 3 months. Where is the customer service? I request a refund for this defective product.