My phone was buy in velcom, Belarus.
After few months use i have trouble whith adjust volume ring sound. When volume sound ring set to max incoming ring may be very silent. When i change volume pressing key incoming ring don't changed. After restart my phone volume return to default. I don't use external sound for incoming ring and alarms(SIM1 - SunFun, SIM2- Nokia Tune, alarm - lapetus, Clock alert 1) Sometimes lovume very loud with adjusting volume to min.
When i listen music or watch youtube sond excelent, volume adjust work fine.