I have a customer with a lot of extensions (ie, over 100). On calls to Auto Attendant there is up to 10 seconds delay before the prompt is played. Can this be fixed?

Yes, it is a known issue for the customers with significant amount of extension (more than 50). To fix the issue, please open the account with configured Auto Attendant and enter no_cache_ext into the description field. It will disable extensions caching and decrease post-dial delay in calls to Auto Attendant.