Call Automatically Disconnects When Calling I have a android tablet with android 5.1 lollipop in which I have an airtel number.
When I call someone using my number (not WhatsApp just normal call),  sometimes it shows &quot;Dialling&quot; and then automatically call ends in 1-2 seconds. Sometimes, it directly disconnects in 1-2 seconds.
Last thing I remember was that I was playing with some of the dial codes of Android. From then this problem started. Before that, I was able to make calls with the SIM which I have now &amp; also with my old SIM
So this is weird, but I realised that I accidentally dialled *31# and the problem started. Now, I dialled #31# and I am able to call.
For information on USSD/MMI Codes see this wiki page