Literally anyone can claim to be a Professional Dog Trainer - the industry is completely unregulated.  Therefore, before hiring a Dog Trainer, carefully research their education, experience and methods to ensure they are positive and science based.  

Many so called Dog Trainers practice outdated, ineffective and often harmful techniques - often based on discredited theories of dominance, and/or depend heavily on aversive equipment such as prong,  choke or electric collars that serve to suppress behavior not change it.