problem with zone rate

I receive many orders to the site with shipping at $0.

China Post by Air Worldwide 14/21 Days >2KG zones2

Shipping Method: China Post by Air Worldwide 14/21 Days >2KG (The shipping rate cannot be determined at this time):

But china post is only for under 2kg .

if the order over 2kg so you see this massage (The shipping rate cannot be determined at this time)

Fast shipping - 0-100KG
Shipping Method: Shipping via DHL/FEDEX/UPS/TNT Worldwide 5-9 Days (Shipping to GB (1567.00Gram(s))):.

Shipping via DHL/FEDEX/UPS/TNT Worldwide 5-9 Days zones

But people choose the option of Shipping Method: China Post by Air Worldwide 14/21 Days >2KG (The shipping rate cannot be determined at this time):

I can not send orders to people they did not pay shipping.
when they over 2kg they must choose - Shipping via DHL/FEDEX/UPS/TNT Worldwide 5-9 Days zones

How to reslove the problem ?

Thank you .