Customer Service - Unauthorized Recurring Charge

My checking account has a recurring charge for some type of subscription that I did not authorize. I did have a Lindedln account for a few months but I did not use it so I canceled it last week. Someone has apparently gone on my account and did use my Master Card Debit Card to order this without my permission. On my statement the charge was for $32.01 on 11/31/14 and 12/31/14. It says Lindedin Please let me know how I can get this refunded. Gretchen Johnson