GRANDSTREAM GRP2616 6 Line IP Phone, 6 SIP Accounts, 480x272 Colour Screen, HD Audio, Integrated Bluetooth+WiFi, Powerable Via POE

These phones stop ringing after a few days to a week after last reboot if you upload a custom (normal) ringtone. If you are satisfied with a ringtone they ship with (non are suitable for an office environment) or reboot the phones daily (not acceptable with a large office) then they will ring. Support has no clue apparently how to fix this as they have released about 5 firmware updates that "fix" the issue only to have the phones stop ringing like before.If you want ringing phones that sound like a normal phone then buy something else or the older Grandstream phone line.

I bought these to replace an older Grandstream on RingCentral. I fiddled with the settings on the web interface, and got it to make and receive calls. The other party could hear me, but I couldn't hear anything. After digging around, and even copying the settings from the old phone, I thought the phone was broken. Then I noticed the NAT was set to auto. I turned it off. Instant fix. Wasted a few hours, but I'm a law guy, not an IT guy. After that, no issues. The large screen is nice. The sound is perfect. Everything I do is speakerphone, and it sounds like the other party is sitting beside me. Built in noise cancelling so the other party can't hear my printer or any other small noises. Couldn't ask for more.