deal with sb
phr. v.. A2 Elementary Oxford
phr. v.. To interact with someone, especially as part of your job or a specific task.
phr. v.. To interact with a person, especially in a professional or transactional capacity.
I deal with customers every day.
As a manager, she has to deal with many different types of people.
The diplomat was praised for her ability to deal with intransigent foreign leaders without compromising her country's core principles.
Usage
The object is a person or group; the phrase can be neutral or imply the person is difficult.
Teaching tip
Contrast this with 'deal with something', which means to handle a problem or task, not a person.
Pitfall
I deal the customers.I deal with the customers.The preposition 'with' is required to connect the verb 'deal' to the person you are interacting with.