My CitiAA VISA card was canceled with both telephone and email notification. I told them I had autopay and some recent unposted transactions. Citi said if there was a question about the validity, they would call to confirm. I was not called and all transactions were posted and/or transferred to the new card number billing, even a subsequent autopay.
I think Citi handled it well. The slight inconvenience I had was to look over the recent billings and determine the autopays and go online to change them. I'm sure I will find the old number stored with some merchants. But the good thing is that the EXP date on the card was 05/09; so any I miss will have to be updated in any case.
I was on the road using the card when notified; so it reinforces my rule to always have [at least] two cards with me. And since I have had two[sic] much experience, after the first loss of both, I make sure all my cards are not together.
Like brp mine is the SPG AmEx card (as good or better for AA miles); and I add a third CapOne card for use with foreign currency to avoid the bank surcharges.