How can we save excise duty on indirect export

How can we save tax on indirect export? We got an order from foreign country for steel piping material, we situated at gurgaon and we pass on the order to the manufacturer situated at mumbai, as we are neither manufacturer nor registered in Excise Dept. We are registered in VAT/CST, Service Tax and having the IEC code for import and export. We usually imported goods from foreign country and export to foreign country as well. Further, I know that Export is free from all type of duty, but being a merchant or indirect exporter this time, our mumbai vendor (will export final goods on our behalf) will raise invoice to us with charging us excise duty of 12.36% and upon giving him a Form H, he will not charge VAT/CST to us. So, in this case, I want to know that how can we save excise duty as well, being a merchant or indirect exporter??? our vendor in mumbai is registered in excise as well as in VAT/CST and Service Tax also.