Dual Way Window Intercom System Anti-Interference Window Glass Speaker Bank Counter Intercommunication Microphone System Voice Interphone for Store,Office,Hospital,Securities Company,Restaurant

i bought 4 items of this product , when I opened product and installed but one of the purchased not working ! I mean one of the purchases! on of the intercom coming very loud noise when we started working ! I sent a text to the seller and I said please exchange for me or send a new one or refund of one of the 4 purchases ! and after many days nothing happens ! what’s wrong ! i trusted then I purchased , and now I have problem and nobody don’t say sorry and nobody answer ! I’m wait a bit more , then if nobody didn’t follow my request I’m going to complain !

To much feedback cannot hear good. Quality isn't what I expected