Your phone can announce your incoming callers by name if you enable the “speech for phone accessibility” option that is found by going to Settings > ease of access > tap the ON/OFF toggle:
When the “speech for phone accessibility” toggle is turned to the ON position the phone will announce the name of the person who is calling you if the person’s phone number is found in the phone’s people hub, otherwise the phone will announce the phone number of the incoming call.
NOTE: If you don’t find the “speech for phone accessibility” option when you go to Settings > ease of access then your phone (make/model) does not support the feature and you won’t be able to use the feature. The “speech for phone accessibility” feature is regionalized, which means it is not available worldwide, and the feature must also be enabled by the OEM and/or carrier before it can be used.
The feature is available on Windows Phone 7 and 8.