Vat & service tax - implications (on sub-contracting)

one point to be noted is that whether B issues invoice to A or not for the service given and spares cost. If yes, then vat & s.tax on such bill will be input credit for A and A can charge from customer for such spares and services including output vat and s.tax.

If no invoice issued by B, then A can directly issue invoice to customer and cost of spare part will be treated as stock transfer.

Invoice will be issued at each stage/leg of transaction by respective ASC. Request all to please share your views of VAT & Service Tax applicability on each transaction separately.

There is no body who can reply to this query ? 

Compnay X sells its product subject to 1 year warranty and after expiry of said warranty,  some issues comes up with the product.  Since warranty period has expired, Company ask its customer to get the product repaired thru its ASCs network (Authorised Service Centres). Now transactions happens in following order : - 

1. Customer approaches ASC - A (New Delhi)
2. ASC accepts the product for repair (Out of warranty) on paid basis.
3. ASC could not repair the product and sends it to ASC-B in (New Delhi)
4. ASC-B, repairs the product (changes the required part & incurs labour) & returns it to ASC-A
5. ASC-A delivered the repaired product to Customer    Now the question is what will be tax implications (VAT & Service Tax) on each of above transaction,
    please share your views.  And what if the ASC-B is situated outside Delhi ?