In the Name of God, the Compassionate, the Merciful.
Hi!
Man: So I take 7C to Front Street and then I transfer to 11B. Ticket Seller: Right. Man: And then I get off 11B at the airline office. Ticket Seller: Right.
To me, it appears as follows:
The man wants to confirm that he catches 7C and leaves for Front Street, and then he catches11B and leaves for the airline office which is his ultimate destination.
‘To’ means ‘leave for’, and ‘at’ means ‘the exact point’ of destination (the airline office) where he will be dropped.