excise invoice

Hi all,

We are using Customer Service module, I have proble regarding invoice.

We create service order against equipment, which includes number of components for issue, say a,b,c,d

We issued the material against service order by tcode : MB11, by which a material doscument is create, with mat. Document we create excise invoice through J1IS,

But now we are getting two different excise invoice w r t material list. A & b in another invoice and c,d in another invoice.

Can anybody please explain what is the problem why system creates two invoices ?

And how to resolve this issue ?