I'm sorry I have been not up on why your trainer wants to discontinue training your pup. I am making an assumption and thinking that this trainer is new to training and probably doesn't train out of a large club but probably from a local dog store setting. Please correct me if I'm wrong.

However, if the issues that make the trainer want to abandon training your pup are behavior related, then you are better off finding a behaviorist to work with instead of just a trainer. Behaviorists will offer you advice on how to correct situations that trainers are not qualified to deal with. They still offer basic training issues but training on correcting behavior issues. You can then proceed with obedience work or whatever venue you choose after the behavior issues are addressed.

I have been training dogs for over 25 years and if it is just a stubborn hard to train dog without issues then it is something I would not give up on. Personally I would find it a challenge I would welcome. There are many trainers out there who will work with you but I should state up front, only if you show that you are willing to work with the dog. I get very frustrated with owners who only bring their dogs in for help once a week but don't follow through with any of my suggestions during the week. It doesn't show a commitment on their part to really wanting to help the dog.

If you need a behaviorst you can contact your vet for suggestions or contact some of the local obedience clubs in your area. I would not contact some of the dog stores that teach obedience since these tend to be limited in their range of services. Most obedience clubs have volunteers who are committed to dogs and have a wide reference of trainers and obedience instructors at their disposal through many venues of dog activities such as class, showing, etc...

If you are not familiar with clubs in your area you can go to the AKC website and find club listings for your state and area there. These are probably the places I would start with since they have active affliations with many people showing in the various dog venues.