SIM auto reconnect to mobile provider / only one GPRS-channel for calling?

Hi all,

I have my Meizu M8SE 8GB since january. I still have the original firmware 9.3.9, because I don't want to lose connection to provider for receiving callings or sms - if this problem is fixed, I will change firmware immediately - I have seen videos and so on and I think it have a perfect UI

Last days ago I got the problem, that my meizu loses contact to the SIM, so I have to input my PIN again to reconnect to the provider.
On my old nokia I have the same problem with the SIM, but it reconnect automatically to provider again - only on beep apears and then it do an auto reconnect.
In my case with my meizu now it's bad, because if I don't have a look at the screen, I don't notice it, that the phone lose SIM contact and also connecting to the provider - so I will lose callings and sms
If there is no chance to get an auto reconnect with SIM PIN recognizing, I will buy a new SIM card.

My second question are the GPRS calling channels: My old nokia has 2 channels for calling. So if I am calling and get another call, I will see and hear it in the background. With my meizu now, there seems to be only one calling channel - if I am at calling another caller will get a busy signal. Also it's bad, because I can't notice it, if someone has called me between my last call

Greets, and thanks for answers in advance