Here is the full email customers received:
Dear Apple Customer,
Thank you for your recent Apple Store order. We appreciate your patience and apologize for the inconvenience caused by the delay in your iPhone activation.
We are still resolving the issue that was encountered while activating your iPhone with AT&T. Unfortunately, due to system issues and continued high activation volumes, this could take us up to an additional 48 hours to complete.
On Monday, you'll receive an email from Apple with an iTunes Store credit in the amount of $30. We hope you will enjoy this gift and accept our sincere apologies for the inconvenience this delay has caused.
Thank you for choosing Apple.
Sincerely,
Apple Online Store Team