Bring Jax Back Home

Update : I've just been updated I only have until Wednesday, the 21st to get the money to him or I won't be able to get him.... PLEASE HELP ME :( 

The owner has agreed that if I gave him the $2600 that he originally paid for him, that he'd give me my dog back. My dog was given to his old owners that had him for a month when I first got him. When I called the animal shelter they told me he had an old chip from when he was 3 months old and that they had contacted the owners. I said he was given to me they told me to bring in documents and paperwork proving ownership, however when I got there, they gave him back to the old owners and told me to leave.  I've been training him as a Psychiatric Service Dog since he was 5 months old, I've had him for about 7 months now...  I contacted the old owners and they told me they won't give me my dog back unless I gave them 2.5k. Originally they only asked $500 for him. They had to get rid of him because they were going to get evicted from their apartment as GSD are a restricted dog breed. They literally said "good riddance" when I had got him. When I first got Jax he was emaciated and afraid to be touched. He would literally scream when someone touched him and I have proof that he was being abused . I've contacted the supervisors at Dewey animal shelter just to be screamed at and hung up on.

Jax is now in his old abusers hands and I have no way to get him back despite vet records, him being on my lease, countless pictures and photos of him, proof that they were selling him and rehoming him, and a prescription from my doctor prescribing him to me as a service animal. He is currently a SDiT for my PTSD and Anxiety. 

How he ended up in the shelter? Well I needed somebody to foster him for about a week. I was having family trouble and moving things in and out of my house and I didn't want to risk losing him. I had found someone who offered to watch him for a few days. She ended up leaving him alone in the house for 10 hours and when she came back, he had torn off the blinds by her front door. From then she drove him out to her parents house who live an hour away from me, and told me I'm not getting him back until I gave her $200. She ended up dropping him off at Dewey animal shelter and now he's gone.  

I am completely destroyed. They don't care about the well being of him. They just want money from him. Or even worse, since he's not fixed they'll breed him. He misses us dearly.

But what's worse is that he will be abused and neglected, and I can do nothing about it. I've lost my baby boy, and I can't do anything to get him back.

Update: Many of you keep telling me to go to the police, I have, I've called them seriously 6 different times in hopes I would get in contact with a different officer that would give me some insight. Nothing can be done because of the microchip.... She said I could have never in the beginning switched the microchip over to my name in the first place because he needs to be there to do it. Theysaid it's a civil matter but they agree that the best way and easiest way to do this is to get the money and once he is in my hands and registered under my name I can turn around and sue them for boarding,care, training etc. Because if I were to take him to court he will hurt him or make sure I'd never be able to get him back before I'd be able to actually fight him in court. All 12 people I have talked to in law enforcement areas and animal control have said this. Nevada has a major flaw in it's system as far as microchipping goes.