1. Browse to 192.168.0.1 in a web browser.
2. Use admin username and password which should be found on the routers label. (Unless it was changed by a device admin at your company)
3. Click the Firewall tab in the left-hand column and set the firewall level to Maximum. If there is a save/apply option, please click that.
4. Click on the ALG tab in the left column.
5. Click the SIP ALG option off then save/apply
The router may have to reboot. If you reboot the device, all items will lose internet until the device reestablishes its connection.