Hi,
Do you have AT&T mail set up in your Outlook client? If so, which version of Outlook are you using? Please first check the Deleted Items folder in your Outlook and see if you can see your contacts. If there is nothing in your Deleted Items folder, we can also try right-click your Contact folder and select "Recover Deleted Items" from the context menu. Check if you can find the deleted contacts in the Recover Deleted Items dialog.
If you don't use Outlook as your email client, I'd recommend you contact the AT&T support for further assistance.
The reason why we recommend posting appropriately is you will get the most qualified pool of respondents, and other partners who read the forums regularly can either share their knowledge or learn from your interaction with us. Thank you for your understanding.
Regards,
Steve Fan
TechNet Community Support