Help please I can’t make a call or receive

Hi Patpear_3026732 
Even though your phone shows '4G' as the preferred network this doesn't mean that you can connect to it.
4G is just the name used in phones as a label for the 4th generation network but the actual technology being used is VoLTE (Voice over LTE).
To be able to connect to this network and be able to make/receive calls you have to enable and turn on VoLTE (also seen as 4G Calling in some phones) in your settings.
This is a link to the 8200 model (as you don't state what model you have) and will hopefully point you in the right direction as to whether your phone has VoLTE turned on and if not how to do it....
https://www.three.ie/device-support/device/doro/8200/topic/network/how-to-activate-4g-calling

474747 you say 'I am experiencing the same issue with not being able to place calls, and calls cutting out randomly'. 
Again, check that you have VoLTE/4G Calling enabled on your phone (Internet search engines are your friend to show you how).
Having calls cutting out suggests that you do, unless this is happening when you are in an area that still has 3G coverage and your phone is connecting to that instead.