Unless it's discussed with you beforehand then any substitution (unless, somehow, it's even better than you'd ordered and it fitted with the potential medical need you'd ordered it for) is completely unacceptable in my opinion. Anyone could send you anything, if that was alright. Dispute and they'll get in touch almost immediately to sort it out, in my limited experience.

What do they want an image of? The fact that it's weed not hash? Sounds weird. You can't send photos via PM/DM so posting to an image hosting service then sending a link is definitely a thing, but I don't see how that's relevant here.

You are entitled to get what you ordered so you can dispute if unresolved.

If you are unable to resolve with the vendor, you can raise a dispute, click on the order and the dispute button is there.

What's the first letter of the vendor by chance?