I have seen dogs as young as 2-3 months and as old as 14 years old be trained. So the age old saying that dogs must be trained when they are pups is kinda half true. In reality they can be trained at any age :)
If you are looking for a dog behaviorist, check out this page on FB
Happy Dogs
Houman is a dog behaviorist. He solves alot of unwanted behavior in dogs. The aim of the training is to teach the owners what to do.
Usually it takes one lesson to solve the problems. Depends on the owners to follow up on the training taught by him.
You can contact him at 017-611-0966 for more info.
Cheers!