I made the following booking with confirmation:

JFK > ICN Economy
ICN > HKG Business
NRT > SEA Business

However now i want to change the JFK > ICN from economy to business but the first agent i talked to said I have to cancel the entire itinerary in order to rebook the correct class + mileage differences + 3k/pax penalty. The only problem is my last leg that is all booked out already so if I cancel there will be a chance that I cant get that leg back in the same class on the same date.

However I called up again today and the agent said that I have 2 options, first is to cancel the whole itinerary like the agent before and second I can change ONLY the first leg of the segment from economy to business. He stated that this is standard procedure and anyone telling me otherwise was wrong. He said this with confidence and after confirming 2-3x what the other agent told me, I can modify my trip to a new class without having to cancel. He even pointed out that all calls are reported and this is nothing new.

Does anyone have data point that confirms this? I'm afraid of transferring 41k points over and be stuck with it because they cannot modify only 1 leg from economy to business.