If you are experiencing ghost calls on a Grandstream HandyTone Adaptor you can follow the steps below in order to prevent this from happening. 

1. Find the IP address of the device. To do this, you will need a computer that is connected to the same network the VOIP adaptor is connected to. The best way to do this would be to run an IP scanner on the network in order to find the IP address of the adaptor. One such IP scanner can be found here for Windows or here for Mac.

2. Once you have the IP address you just need to copy this, paste it into the URL search bar on your browser and hit enter.

3. Once you do that you should be greeted with this page: 

The default username and password should both be: admin  

4. Once logged in, click on FXS port on the top-right menu.

5. About halfway down the page, enable the following setting to only allow calls to be received from the SIP proxy

6. Scroll All the way to the bottom and click on the "Update" button at the bottom of the form.

A couple of notes in regards to this. You need to access this page on a computer that is on the same network as the phone. Additionally, these changes must be saved when the phone is NOT engaged on a call.