As rightly said by scott, NLP is a very effective tool when we we talk of learning which involves a transformation process just accent tuning wherein you have to work to change your mental conditioning. Quite a few people have expertise in nlp in india like upkar chhibber and internationally richard bandler, you can find no of books written on the subject. likewise there are many professionals,… we have couple of NLP experts here in UK.. but for india you need to make an effort.
What I can conclude is hunting a NLP trainers is worth if one is serious in accent training etc specifically for indian call centers..
Wish you best of luck