Avast changes Firewall from Private to Public

Since using Win10 Avast keeps changing my Firewall from Private to Public. I attach some Screenshots to show what happens. My Internet supplier Virginmedia say they cannot do anything about it as it is Avast that conrols my Firewall.
Why does this happen and how can it be stopped occuring?. I was told only Avast and McAfee do this.
Is the answer to change Antispyware?

what firewall are you using? … screenshot seems to be from your router?

what avast program are you using?

avast free does not have a firewall

Firewall FAQ >> https://support.avast.com/en-eu/article/Antivirus-Firewall-Application-Rules

Hi Pondus,
I am using Avast Premier. I understand that Avast controls the Windows Firewall.
It ws Virginmedia who seemed to think that this is all about the Firewall.
Frankly, I am not really very knowledgeable about these things and to a large degree am groping around in the dark.
Virginmedia also said that this problem only seems to appear with Avast and McAfee.

Regards,
Keith

To help you understand better, take a look at the screenshot attached below:

Picture is from the firewall settings graphical user interface (program) of Avast Internet Security. You configure your Private or Public settings here for either Internet Security or Premier. I believe Pondus is correct, above is from your router, not from Avast Premier.