For shipping from China to South Africa, several logistics companies provide both air and sea freight options, including door-to-door services. Here are some reliable shipping agents you can consider:

1. DHL Global Forwarding
   DHL offers reliable air and sea freight services from China to South Africa. They provide door-to-door delivery, customs clearance, and a wide range of logistics solutions tailored to your needs.
2. Maersk Line
   As one of the largest container shipping companies, Maersk offers sea freight services from China to South Africa. They have a strong presence in both countries and provide end-to-end services including freight forwarding and customs clearance.
3. DB Schenker
   DB Schenker is a global logistics company with a strong network in both China and South Africa. They offer air, sea, and land freight services and can assist with customs clearance, warehousing, and delivery.
4. Kuehne + Nagel
   Kuehne + Nagel offers air and sea freight services, with expertise in international shipping from China to South Africa. They provide full-service logistics, including customs handling, warehousing, and distribution.
5. CMA CGM
   A global shipping giant, CMA CGM provides sea freight services from China to South Africa. They have extensive routes and options for large and small shipments, along with the necessary customs clearance support.
6. TNT Express
   For express air freight, TNT (now part of FedEx) offers reliable shipping services from China to South Africa. They focus on fast delivery and provide tracking services, customs clearance, and door-to-door delivery.
7. Sinotrans
   A well-established Chinese logistics company, Sinotrans provides both sea and air freight services to South Africa. They also offer customs clearance and full logistics services for international shipments.
8. Agility Logistics
   Agility operates both in China and South Africa, offering sea and air freight services. They provide supply chain solutions, including customs clearance and warehousing services for shipments from China to South Africa.
9. Panalpina (now part of DSV)
   Panalpina, which is now part of DSV, offers international freight forwarding services, including air and sea freight from China to South Africa. They are known for their tailored logistics solutions.

When choosing a shipping agent, ensure to confirm their transit times, rates, and the specific services they offer, such as tracking, customs clearance, and door-to-door delivery, to ensure the best option for your needs.