Payment methods question

Hi, i have bought the FF14 from the Square Enix store (not Steam) sinse there was a big discount and now that my subscriptions ended i have a question regarding renewal. Can i somehow renew subsription throgh Steam payment? It is way cheaper in my country to pay through steam because of regional prices. Do i have to own Steam copy of the game to pay this way and its not possible to pay through steam if i bought the game from Square Enix?

I don't think you can. Not being cheaper in some countries is to prevent people in other countries from pretending to be from the country where it is cheaper, but SE is aware of it being a problem.