At 6 weeks old that puppy should be with his momma and siblings..
Why would they adopt out a 6 week old???
How could they give you the wrong dog? I'm confused.
You go to the shelter.
Pick out a dog.
Meet with the dog, decide you want it.
Fill out appropriate paperwork, get approved, pay.
They bring out dog.
If it's not the dog you picked out, you would say "Hey, wrong dog pal." They would bring out the correct dog.
You go home and live happily ever after.
How could you get the wrong dog?
I don't understand what your saying, sorry. Give us more details and I'm sure we could help out more!