Contact. Get In Touch. Call Us(02) 8022 8000Emailsydney@gnaustralia.com.auAddressLevel 13,333 George Street,Sydney NSW 2000 Send Us A Message. Please enable JavaScript in your browser to complete this form.Name *FirstLastEmail *Comment or Message *Send Message Geoffrey Nathan has the tools and expertise to provide a complete end-to-end contract management service for our clients.