The sentence "How may I help you" should be changed to "How may I assist you" in the service industry. Do you agree or disagree? Justify your answer.

"Assist" is the perfect word to use in Customer Service Industry.
I strongly Agree!

Agree, Phrase "Help" may deliver a negative message to the customer as he is week or don't know.
Phrase "Assist" is more positive.

We can use both phrases.
Both of them are in the polite way but the degree of politeness is high in "May I help you." in official works.

It is one thing to ask a lot of questions as a customer service representative.
It is a skill to be able to understand the right questions to ask.
The question is not like this , can be How can I help you?

I guess the take is that if you say How may I help you? the customer actually expects you to wave the magic wand & fulfil their wishes which is not possible most times in real time.
But If you instead use How may I assist you? I think it basically reflects that I am there to find which ever solution available with Us (service provider) however, it may not be applicable to satisfy the customers actual need.
So its like, you listen to a very good sales deal & at the end it says terms & conditions apply!!! We all do the best to deliver excellent customer service but there are limititations to satisfying customer needs.
:-) So How may I assist you? is more professional & courteous.

Yes, I agree to the amendment to the"How may I assist you" ,Because it gives the impression of good service and a desire to help

Agree.
Assist - indicates that the customer is already empowered to do what is required and the rest is a verbal service transaction between the customer and the business.
However - bear in mind languages, Linguistically, some people may find "How may I assist you?" more difficult to say than "How may I help you?" Try it, you have to pause slightly longer for "How may I assist you? to make sure that the 'assist' is heard clearly.
It could be mistaken for "How may I assess you?" depending on the person saying it.

it is not the question of help or assist , the real question is how can you help or assist to get the customer satisfaction , from the customer's point of view help or assist doesn’t matter as long as he will get exactly what he needs .

It doesn't matter if its first or second option in the service delivery industry, all which needs to be focus and to realize the customer is that you should be the front one who understand the real needs of the customer and you should be the one who will respond to his/her concern with OTR (On-Time Ticket Resolution) concept.
Syed Waqas Saghir Internet Marketing Expert, SEO Consultant, Social Media Evangelist.

I am not agree this Is incorrect

May I help you this phrase is agree if used