We were very early into the cancellation thing but I did it completely over the phone.
The only difficulty I experienced was we had purchased our FC tix very early due to a sale situation and when they said they’d make the refund back to our cc I didn’t recall we had cancelled that credit card. When a week went by and we hadn’t seen the refund show up I checked the old card and sure enough - there sat our rather sizable credit. Citi was very good and within three days they direct deposited it into our bank account but I have a feeling had I not been proactive in looking for it, the credit might have sat there forever.