Paytm — missing product in my order

I had ordered an earphone (Tagg Inferno Bluetooth headset), Order ID - [protected], seller name - VSM India Enterprises. Today I received it. But the seal of the box was already broken. There was no headset. Only the box. I had never expected such type of fraudulence from Paytm. I think there's nothing I can do to get my product. I've called Paytm helpline. They said they'll investigate the matter and call me later.
I know what's exactly going to happen. They'll ask if I have any proof. They might say that they don't believe me. I don't think I'll ever get my product. please, someone tell me what should I do now.