My BV6000 has been working ok as a duel sim phone. Sim 1 as the main and Sim 2 on standby.
Both Sim Card signals were showing in the top Sim1=4G & sim 2=3G. both were receiving and making calls. Both simcards are 4G

Last 2 days only ONE simcard works for signal phone, calls and data. The second Simcard shows no service…Emergency calls only. (Apparently Optus Australia changed and there is no 2G network).

BOTH sim cards are working with different imei numbers showing up in Status/About phone. So I do know that the Phone is recognising them.
I am on
Build = BV6000_Blackview_¬V01_20161011
Android version 6.0 Security patch level = 5July 2016
So… my questions are (Please answer as 1, 2, & 3). :
1. Is there an update for my Phone to fix these issues?
2. Is there a Patch for the second simcard to be able to make calls?
3. If it cannot be fixed… is the BV7000 in the same boat.
4. Will the BV6000 update Android version 7 fix this? ( have asked previously different thread re: upgrading to Nougat 7.1)
Thanks in advance Mick

Sorry I can not reproduce this issue on my test device so I have to ask you to try out to update to the latest Firmware and perform a factory reset in recovery after that.
wipe data/factory reset in recovery (this will delete your data/settings):
- Power off and then press Power and Volume up together for around 10 Seconds
- be sure that the little arrow point on recovery (select with volume up, enter with volume down)
- Then the open android with red triangle+"no command" is shown press Power and Volume up together again
- Select Wipe data/factory reset with volume keys, confirm with power
- After factory reset select reboot system now

Please report if this solved your issue or not. If it don't help you could easily flash back to your current version.