Shared office space

At the moment I work from home but am considering moving into a shared office space (one other person who works in a completely different field).

I'm happy that I can deal with security of files and electronic data, but I'm trying to work out how I could protect information that she might overhear when I'm on the phone.

I have asked the Institute and they have told me to take legal advice.  Thanks for that.  

Has anyone else had a similar situation?  And if so, how have you dealt with it?  My thinking is that a non-disclosure agreement should do the job if drafted properly.

Thanks in advance.