It does have to be done through TK Miles & Smiles, there is no such thing as a centralized Star Alliance award reservation center. It may have just been an issue with English communication which is something also you'll encounter often with TK reservations on the phone. I'm not entirely familiar with Miles & Smiles but do they have a different phone number to call for partner awards than TK metal awards? If you're near a ticket office then just go there, if not then call one in the UK or US (assuming you prefer booking in English).

Another problem I see is that if I recall correctly, you can only book one way flights on TK metal, partner flights have to be round trip. Of course you can still book a round trip, use it like a one way and throw the second half away, that's your choice.