Dear Blackview Team,
I have bought the BV7000Pro device in november 2017, phone was excellent and i was very satisfied but the last month occured a strange issue.
1.) When in call suddenly i cant hear the other person or he cant hear me.
2.) When i start a call it freezes and if i press call termination it freeze with the messagte "Hanging Up"
3.) When somebody is trying to call me it says that i am not available but i have full signal.

All this problems can occur randomly, sometimes phone work normally.

I had update the phone to Android 7.0 but it did not fix the problem.

Waiting for your reply ASAP because i work through the phone a lot.

With kind regards
Ruslan Yefimets
Alfa Greece CEO

Hi there. It looks like a faulty internal antenna connection. 
To rule out if it's a software or an hardware issue, please perform a factory reset, don't install apps, try the phone and report back.