A dealer can label their weed anything. Most of them don't even know what they're getting and make up names to move product.

The only way to 100% know, is to order the seeds from a seedbank, and grow them yourself.

Another helpful way of knowing is buying from growers. Not only would you be told what strains they're growing, but it is much cheaper, fresher and yummier. I buy right from a grower and he goes on forever telling me about new strains he has, and the weed ain't bad either.