I know how you feel... I just quit my job about 2 weeks ago, went through a similar things
Here's a classic example of how things went most of the time.
Customer: I want to warranty this product
Me: sir this is not our product it's not even our brand, goto the brands store get proper warranty
Customer: Impossible, I bought this product here and I expect warranty now.
Me: well do you have a receipt.
Customer: Of course I don't have a receipt who keeps these kinds of receipts.
Me: just a sec I'll see what the boss would do in this case.
Me: Boss client wants to warranty product we don't even sell and he doesn't have a receipt can we warranty it anyway.
Boss: NEVER what kind of place do you think this is, we don't work for free and just give away stuff. ABSOLUTELY NOT.
Me: oK then, sorry sir we can't warranty it
Customer literally blows a lid and I though he would pull a gun and shoot me on the spot.
Me: Boss can you come and deal with this, customer is somewhat agitated.
Boss: Sir we'll warranty this right away this time no problem.
Me: confused ???
Later
Boss: You don't have enough experience to deal with customers.
Me: WTF