refund

I downloaded prezi for a presentation I had to do for a job interview. ..it closed down on me twice ,I lost work and I found it too much to pick up in a short space of time.
I was under the impression that I had closed my account but this does not appear to be the case!
I ended up using power point for the interview as it was more reliable and user friendly. 
Since I didn't get the job (which was the only reason I downloaded Prezi!) I have no use for this programme and cannot afford this payment!
I suffer from chronic pain and am unemployed so this payment has put me further into debt!

Is there any way I can cancel and get a refund?