Bought an “Original” iPhone Lightning Cable from Nehru Place... Apple Store guy said its fake

I bought an iPhone Lightning cable from a shop in Nehru Place. Before buying it, I asked the shopkeeper multiple times if it was genuinely original. I kept confirming because I didn't want to end up with a fake one.
He confidently told me, 100% original.
So I trusted him and bought it.
Later, I visited an Apple Store, and they checked the cable and told me it was fake.
Can anyone can guide me finding if its original or fake?