Hi lan,
Welcome to our forum.
We suggest you block incoming numbers using AudioCodes gateway using the following link, because it will reduce voice flow between AudioCode and SFB server:
http://ucadministrators.blogspot.sg/2016/05/blocking-incoming-calls-from-pstn.html
Note: Microsoft is providing this information as a convenience to you. The sites are not controlled by Microsoft. Microsoft cannot make any representations regarding the quality, safety, or suitability of any software or information
found there. Please make sure that you completely understand the risk before retrieving any suggestions from the above link.
If there are any questions or issues, please be free to let me know.
Best Regards,
Jim Xu
TechNet Community Support
Please remember to
mark the replies as answers if they helped.
If you have feedback for TechNet Subscriber Support, contact
tnmff@microsoft.com.