Hello Prapaporn,
After checking with other airlines, my initial proposal is actually the most competitive pricing available this time, with reliable service. Please do consider this is a hazardous shipment.
Also, if the customers still does not approve, please do obtain their target rate and which airline they are basing their target rate from. Please also make sure to provide the routing and total transit time. And we will try to approach the same airline at my end.
If you have any questions or concerns, please let me know.