All though you are able to configure a Third-party device, our support is very limited. The only information which we can provide for these devices are below.

Please note that Setup and quality of calls cannot be supported whilst using a third-party device and we suggest either purchasing a handset or alternatively using our PC and Mobile applications.
For userid and password, this can be found under your extensions profile. Go to Manage Devices section. Click View

Click “I Agree” after reading warning and terms of services

Window will appear with extension registration credentials.

Please Note
This does not mean your third party sip device will work out of the box, most sip devices are blocked, and require to be unlocked from our support department, if you believe you have setup your generic sip device correct and it's not registering, getting a 408 error, then please reach out to support, to assist
To use the server side DND Codes on your custom device you can set your phone's settings to use the following numbers, or dial them manually
Dial *363 from your device
Dial *363* from your device