Still incurring recurring charge after downgade to free edition

Still incurring recurring charge after downgade to free edition

05/14/2013 I downgraded to the CRM Free Edition. 
Order Number:  792202000000119001
User: lbrmd1
Email: ggms.1361@gmail.com
I would like a refund for the renewal charge 06/06/2013, order number:  792202000000120001
Why did this happen, and can you prevent it from happening again?
Thank you