I was at OBI two weeks ago and bought something an...

I was at OBI two weeks ago and bought something and after 4 days wanted to give it back then the cashier gave me a note where I should sign, I thought I would get my money back when I signed, afterwards she gave me one Given a voucher, I wore it, after that I couldn't make myself and now I only have 3 months until I can buy something, hope that I don't need anything from OBI