If you called and they told you this, what do you mean "Is there any other way to do it like calling them" ???

Also the limitations of upgrading an economy ticket to Business using miles are so many (it has to be Y class, needs too many miles) that you would just waste miles / and the most probable is that your ticket is not Y class and cannot be upgraded. Have you read aegean's terms of star alliance upgrade using miles?

You should have checked for aegean award business star alliance availability instead of buying the economy ticket with Turkish.