If this were an exam question, I would advise the student to use the present perfect structure.
The question is in the present perfect, "Who have you worked with so far?" The examiner is probably looking for an answer that echoes the same structure

I've worked with people from all over the world.

The contracted form makes the sentence sound more natural too. In the REAL world, however,

I've been working with people from all over the world

is absolutely fine, people say it all the time. The present perfect continuous tense stresses that the speaker is currently working abroad or has just returned, the progressive tense implies the action is not completed but ongoing.

In brevis, both forms are acceptable and grammatical.

If this were an exam question, I would advise the student to use the present perfect structure.
The question is in the present perfect, "Who have you worked with so far?" The examiner is probably looking for an answer that echoes the same structure

I've worked with people from all over the world.

The contracted form makes the sentence sound more natural too. In the REAL world, however,

I've been working with people from all over the world

is absolutely fine, people say it all the time. The present perfect continuous tense implies that the speaker is currently working abroad or has just returned, the continuous tense emphasizes the action is not completed but ongoing.

In brevis, both forms are acceptable and grammatical.