Personally I use the Mitel 6800 series phones for the majority of my clients… however when it comes to custom rings, there is no support for changing the ringtone per type of call between FreePBX and Mitel phones. So the only way I’ve approached this is changing the cadence of rings for different kinds of inbound calls. Then individuals that sit next to each other can change the ringtones for all “normal” calls on the phones themselves. I haven’t explored this with the other brands that support Phone Apps.