You may want to take into consideration that Sallie Mae is a business, and as such has to pay employees and business expenses and so forth.
Many companies try to avoid allowing you to call them because that one call alone will destroy their profit from whatever you purchased from them. In this case, not only has the Indian call center been flooded, there has surely been a relentless flood of calls to the Consumer Advocate Line, whose employees certainly cost a great deal more. Add to that the expense of cleaning up this mess, it's not as simple as pure profit from people changing payment plans.
As for them making money money from you switching to the level payment plan -- I'm not sure how you came to this conclusion. The level payment plan will pay off your loan FASTER, thus you will pay less interest. So now they're losing money, no?