How to contact the customs clearance department of «DHL Express Türkiye» in written form?

1. For shipments ≥ 150€.

Talimat@dhl.com and sevilay.demirelli@dhl.com.

2. For shipments < 150€.

kategori3@dhl.com
Whats does mean «KATEGORİ 3» for customs clearance in Turkey?