Is your binding configuration set to allow large data? If you are using an httpbinding you should configure your endpoint and your service in this way
<basicHttpBinding>
<binding name="LargeDataBindingConfiguration" closeTimeout="00:01:00" openTimeout="00:01:00" receiveTimeout="00:10:00" sendTimeout="00:10:00" allowCookies="false" bypassProxyOnLocal="false" hostNameComparisonMode="StrongWildcard" maxBufferSize="2147483647" maxBufferPoolSize="2147483647" maxReceivedMessageSize="2147483647" messageEncoding="Text" textEncoding="utf-8" useDefaultWebProxy="false">
<readerQuotas maxDepth="32" maxStringContentLength="998192" maxArrayLength="2147483647" maxBytesPerRead="4096" maxNameTableCharCount="2147483647" />
</binding>
</basicHttpBinding>
Other then that try to increase on your server the maximum length of content in a request supported by the IIS
<security>
<requestFiltering>
<requestLimits maxAllowedContentLength="4294967295" />
</requestFiltering>
</security>