Talking of Mumbai-
Could never get them to make correct calls re including call sign- Had this conversation or similar many times-
Me- "Mumbai, Emihad 123 request descent"
Them- "Descend to FL250"
Me'" Confirm Emihad 123 descend 250?"
Mumbai- "Affirm"
Me-" Confirm it was Emihad 123 you were saying Affirm to...."