Originally Posted by SK AAR

In principle the upgrade should include both segments, but I can easily imagine local agents denying this and prepared only to upgrade the first segment/leg that they are handling (either due to ignorance or incompetence). My suggestion would be take this discussion upfront with the agent - perhaps even with a supervisor. Accepting to be upgraded for the first leg only and expecting to get this resolved upon arrival at IST is bound to fail - as already reported above the IST agents will not touch/couldn't care less if the pax has only been upgraded for the first leg.