Call waiting sound doesn't work at Lumia 640 Win10

[Windows Central Question]

When i have a call in process there is no sound to warn me that there is an other call in waiting. The call waiting is turned on. There is no option for set a beep or something else. Could you help me to find a solution?

 

[drmega0226]

Have you tried resetting your phone? I would also check that call volume is all the way up while call is in progress. My guess though is a hard reset should fix the issue. Also, try turning call waiting off, then back on. That helped me once. Hope I was of assistance.