Hello,
I am travelling from Belgrade to Maputo with an 11hr 55 min stopover in Doha. Long story short, on my trip to Belgrade I used miles to upgrade to business class, on the return to Maputo I received an e-mail and paid to be upgraded (was in N, now in I-class). I tried calling Qatar Airways in order to check if I was eligible for (paid or free) STPC. They said they would put in a request. I called back today and the lady seemed confused, saying I would lose my business class upgrade if I chose to pay for my STPC. Anyone with experience?