Makro Not Honoring Returns

After buying an office chair (which was only available online) I put the chair together, and sat in it I realized that the chair is quite uncomfortable and slants downwards, resulting in quite a bit of pain.

I tried to return the chair online and the day the courier was scheduled to collect the chair I was informed that the chair could not be returned due to the box being opened and this apparently contravened their returns policy. I reviewed the returns policy on the website and did not find any text that stated that items need to be unopened for eligibility for returns. When I asked the Makro employee to furnish me with a copy of their returns policy and I'm still waiting for this a week later.