Diego,
I happened to check some more similar cases & tweaking the input gain & output attenuation is the only way forward. Nothing to worry about messing existing call quality, they will just get better if the tweaking of these parameters is done carefully & with lot of real-time testing.
Please note that input gain has values from -6 to 14 in dB which means scale is not linear, and also attenuation negative values of attenuation make signal stronger (volume increased) while input gain positive values are making signal louder. For making signal coming into router stronger (louder) you can use input gain 3, which will cause you will other hear louder. Also please try to make attenuation smaller from default 0 to “-3”, this should make signal stronger .
Pls rate the post if it helps.
GP.