Hi, I've got a Superb iV with and it had the same problem. It's a 23 plate. SE tech. Anyway, I had it booked in to be repaired for this under warranty, then last night the car told me there was a system update available, so I selected to download it (which took a couple of hours) then told it to install (which took 20 -30 mins) and behold the terrible crackly outgoing phone sound is fixed!!!
Another bonus I noticed today is that it will now do Android Auto through bluetooth without having to have the phone plugged it!! Result! Cancelled my repair booking as it's now great!
The screenshot attached is how it is now, since the update.