OnePlus India — promo code not working

When i purchased oneplus 5, they gave me the promo code which i can refer to my friends so that i can benefit from my future one plus purchase. I shared this to my friend who was buying oneplus 6 from amazon. But the promo code what they shared was not working; but he had to place the order without applying the promo code. Upon checked with amazon customer care, they said the promo code was in invalid format.

The format what oneplus gave me was xxxx-xxxxxx-xxxxxx
But the format amazon expects was xxxx-xxxxxxxx-xxxx

Amazon asked me to check with oneplus customer care. Upon checking with oneplus, they said it should be resolved by amazon and they don't own this issue. After explaining the problem, they admitted this is a problem from their side but they cannot map this with already purchased order.

I told them this is not fair; i am lost one of the reference and it should be compensated. They told me they will give me a call back. I received the call back after 3 days; but he said he cannot do anything in this regard.

It is very difficult the get the reference, if we get the reference also; this kind of pathetic issues is really embarrassing me.