Shameless SARS

SARS is being unfair, it is asking me for tax returns for years that I was not yet working (still in school) and to make matters worse apparently I now owe them a large amount of money. I now have a garnish order of over R3000 as well as my normal paye of over R6000. How do they think I will sustain my life. Could they not atleast inform me and give me a chance for a payment arrangement even though I still don't understand how I owe them as I have been paying them since I started working.