How do i contact the billing department.. very unhappy.

I need help with a recent Adobe charge. I was billed $72 for Acrobat Pro, but I never confirmed or authorized this payment.

I signed up for the free trial, canceled it, and did not agree to be charged afterward. I barely use Adobe—if at all—so this charge came as a complete surprise.

Is there any way I can speak with someone in the billing department about getting a refund? I'm extremely disappointed that this happened and would appreciate any assistance in resolving this issue. Thank you.

To also add even when cancelled, I was being billed about twice a month.