Just as others have had some problems with volume on the 524 phones, we're experiencing problems with low volume on the 525 phones. It appears to be very infrequent and on both internal and external phone calls. We're running 7.2.5 on the 525G phones. I have looked at the individual web pages, but I don't see any admin login or advanced pages where I could make adjustments to individual phones. Any help would be much appreciated, especially in getting into the admin pages for individual phones.
ON the Phone, press the MENU button, then select Network configuration.
In this menu scroll down and active "Web Server Writable"
Save the configuration.
You should then be able make the changes I have suggested.
7.4.2 has many improvements around audio issues and at least one known issue that we will resolving shortly. You should experience a noticeable difference. You may also need to tweak the FXO port gain in order to boost the signal and improve volume levels.