Expression: to be through with somebody

[wanderer]

English Error, Elementary Level

ESL/EFL Test #7 "English Prepositions", question 10

I'm sorry to have to say this but I'm afraid we're out with your company because we can no longer trust them.

(a) out
(b) with
(c) because

English Error, Elementary Level

ESL/EFL Test #7 "English Prepositions", answer 10

I'm sorry to have to say this but I'm afraid we're through with your company because we can no longer trust them.

Correct entry: through
The error was: (a) out

You have found the error but your entry is incorrect.
I'm sorry to have to say this but I'm afraid we're out with your company because we can no longer trust them.
_________________________

I didn't understand this sentence, please explain it. Thank

wander

[Pamela]

Expression to be through means to finish smth,go through and etc.
Ex"I don't want anything more to do with you, we're through

In your sentence the very expression means that they(we) break any contacts or links,dealings with the company because of mistrust