We can debate this all day -- particularly if you are talking to someone at Garmin that is incompetent. They are normally crackerjack on support.
If you check the manual (attached -- ooops it is too big for this forum's limits -- try this link
https://buy.garmin.com/shop/store/manual.jsp?product=010-00715-20&cID=134&pID=14926) you will find a section on using the media player (P 28) that discusses pairing a wireless headset. Page 19 covers pairing the phone.
There are two sections in the bluetooth menu -- audio and phone. You pair the Scala to the audio and the phone . . . well, to the phone . . .
Garmin on-line support has suggested that -- if you are having difficulty pairing two devices that you clear out all your pairings and pair the headset first. Once you confirm that it is working then pair the phone.
Sorry you are having so many issues, but this really does work.