For the volume resetting, take a look at your ring group’s settings. There is a “ringer volume override” setting that can be set for Sangoma phones. As for the mic volumes, try modifying the sangoma-default template. In the Options section, you’ll find some Send Volume options. This might work for your situation, but there may be better solutions depending on the issue. For example, if internal calls sound fine, and only external calls over POTS lines have low volume on transmitted audio, I’d probably try adjusting things elsewhere.