I had fraudulent charges on my Cent AC back in June, I reported it on a Thursday and told a replacement would take 7 - 10 days, it was with me the following Tuesday so around 4 days including the weekend.

Roll on to Sept and Amex warn me about more charges going through on the new card, a replacement would again take 7 - 10 days. I had to call them after 11 days and it finally turned 3 days later.