Before flight starts you can only speak with TA about significant changes , as SV cant modify ticket without TA agreement

if SV cant provide what you paid for then TA should rebook you and of course you should agree with change

As ATflyer said ; your only option is to be quick and rebook your journey directly with SV or find a TA in your city who works with SV and ask for a quote

which one is it ? it might not even be a polish one , just the polish version of a multinational OTA