How to remove Attachment lines?

Hello everyone,

I need to remove Attachment lines (ATC1) using SDK.

At the SDK help, I found the following:

"To remove an Attachment item, set its FileName property to NULL ("") and call the Update method of the calling object."

I did that, but when i call the Update() method, it returns error -5002 (path not found).

Does anyone have an idea of how to remove attachment lines?