Hello Joy,
If you can not fix storage charge you should show "at cost " in your offer,rather than 1.75/kg,which mislead us to offer to customer storage charge based on 1.75/kg.For the extra charge,there is no related items showed in your offer sheet, how can i explain to customer?Could customer thought that how much we bill to them and they have to accept it,no offer no standard rate?
I we still insist, i think we have to absorb the extra charge internally by half/half, and we will loss all of their biz.