Did this some 20+ times through their contact center (via e-mail).
They reissued the tickets.
Relevant to this thread - prices one way for Eco - Business upgrades (usually class D) is around 400 Euros.
Other data points:
Upgrades from Eco (E,V,S,T...) to Business (M, I, J, D...)
OTP - MAD - OTP / June 2022 - 730 Euros
OTP - CDG - OTP / Sep 2022 - 810 Euros
OTP - TLV - OTP / Nov 2022 - 890 Euros
OTP - TLV - OTP / Jan 2023 - 830 Euros
OTP - MAD - OTP / Mar 2023 - 720 Euros
OTP - ATH / IST - OTP / Sep 2023 - 500 Euros