Remebering call volume settings

[SystemCraft]

Call volumes are reverting to a default level after every call and not remembering user changes.

I found this Yealink article describing this issue:
https://support.yealink.com/en/portal/kn...1acb02be65

We've checked with the voice provider and they do not auto provision these parameters. Therefore I assume we have to manually edit these.

I found more articles about editing parameters in the Config file. But I couldn't find anything about how to open the config files in order to edit it.

Ie. Is this done via the web interface of the handset?

We use T43U