While I don’t want to derail some epic rants, the real ‘baddie’ here is IB, not BA. The latter has no flights from Quito and would have no staff there to ask (or to decline). As accepting carrier, it was fully Iberia who refused the OP, not BA. (Perhaps moot, admittedly, because a BA agent would have done the same thing, but accuracy in blame is still important.) As has been mentioned, there are plenty of airlines who will indeed send bags through to BA.