Hi,
First off all thanks for kind reply..
Users has latest update for Skype app on iPhone and Android phone. Also they have latest iOS and Android OS installed on mobile.
One of the user has iPhone so i suggest him remove skype for business app from his iPhone and do reset RAM on iPhone and install Skype app, However he did and same problem occur. call drops out with in 3min and 15 sec.
No I haven't done CU update on the server..!! do you think CU update will fix..!!
If you have any other solutions please let me know.
Thanks
Kintal