Sir i am using blackview bv 6000.i am just upgrade Android version 7 ,i am using jio and bsnl Indian network connection after version upgrade jio not supported for incoming and outgoing calls but i can browsing calls only not supported please give me a solution and let me know any setting issues

You may not update successfully.
Please follow the steps and try again：
Enter into setting--about phone--wireless updating--search for the latest version.

I guess he lost the IMEI while update.