Web Services Client - Message Length Limit Was Exceeded - System.Net.WebException

Hi Folks.
I am working with a web service client.
I am making a web method call, and it was working fine. We are load testing a really long message and it threw the Exception below. I have an app.config file, (see below) but I need to know what property to set and couldn't find it.

Also, the publisher of the web service is working with PHP, I believe on Apache, and they tried with a PHP Web Client and it worked - so I don't think it's a server side config issue.
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Exception:
System.Net.WebException: The underlying connection was closed: The message length limit was exceeded.

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App.Config:

<?xml version="1.0" encoding="utf-8" ?> <configuration> <configSections> <sectionGroup name="applicationSettings" type="System.Configuration.ApplicationSettingsGroup, System, Version=2.0.0.0, Culture=neutral, P ...