2k km is a lot; your bike stopped being "new" long ago. Clicking noises happen; what did the shop say/do about it when you brought it in? Barrel adjusters will only turn so far -- has yours just reached the end of its range, or is it broken?
It would help to know what kind/model of bike you have to better understand the quality of its components.
A clicking noise and barrel adjuster issue doesn't seem like a lot to me over 2k km. If you haven't already, you should probably be replacing your chain and perhaps rear cassette.