URGENT: Create Dynamic, Combined MailChimp Lists

Hi Freelancer, I'm looking to urgently (within the next 4 hours) combine several existing dynamically updated MailChimp lists, without changing the original ones, and with the new Master list being updated with new subscribers. We're also looking to stay on the free version for now, so cannot exceed the maximum subscriber list number of 2,000 (one new list contains 1,400 email IDs, so cannot be combined or uploaded via CSV (I think this must be set up via MailChimp API). Please briefly outline how you would approach resolving this issue in 1-2 sentences before interviewing, and add your Skype ID for a quick call to discuss this project further. Best Wishes, Tom