Whatsapp doesn't allow more than 16 mb file transfer.but i'm able to transfer files much larger than that through my iphone 6 plus

Whatsapp doesn't allow more than 16 mb file transfer. But i'm able to transfer files much larger than that through my iphone 6 plus. How is that possible?

It's their rule. They're under no obligation to change it for you. Either live with it, or go somewhere else.

I'm not sure what you mean, you don't transfer files through an iPhone.

As for Whatsapp, so what? They have their own rules for what they can allow/handle.