N to n
The 'obligation' group
These nouns refer to the fact that someone owes someone something or should do something for them.
debt duty indebtedness obligation responsibility
Both acknowledge their debt to him.
They are basically saying they have no obligation to their customers.
Duty, obligation, and responsibility also have the pattern N to n to-inf.
They have a duty to their clients to undertake transactions for them as cheaply as possible.