In case a customer faces the problem of sudden disconnects, the common solution is to adjust the packetsize from 30ms to 20ms. 

Changing the packetsize in the Fritzbox device can be done in the following way:

- Go to the tap "Telephony";

- Click on "Telephone numbers";

- Select the number and click on "Edit";

- Scroll down and click on "Additional Settings";

- Change: "Packet size in milliseconds in send direction" from 30 to 20.