I am trying to update the details availalbe in the "Manage My Settings - Edit Organization Info" section. Please let me know, is there any API usin which I can update the details in this form programatically.
Unforunately there isn't an API call that can add the physical address of your company. That is something that we're going to address in the future, though I can't give a timeframe on when we might release it.
For now, you can send in the organization address in the footer of each email campaign you create or edit through the API. Campaign creation/scheduling is the only time that the organization address is required in Constant Contact.