Sky provide your broadband so Sky are responsible for sorting it out. After all, you pay them for it don't you? They should liaise with BT Wholesale or Openreach to get it sorted.
Only if he's renting the BT line via Sky.
But the very fact that he's spoken to BT Retail in India suggests he's got a BT line with a Sky service independently activated on it. In which case Sky would only liaise with BT insofar as it covers the DSL side of things. When it comes to the copper, that would be between the subscriber and BT Retail.
The unwashed masses cannot talk to BT Retail about a line if its being rented by the SP from Wholesale or Openscreech.