I can NOT switch back and forth seamlessly between my computer (DG10) and my Cellphone (Bluetooth), how do I fix this?

To switch between your computer and your cell phone, first, pause or end the audio / call on the current device (either by pressing the corresponding button on the headphones or directly with the active device). After a few seconds, play audio or make a call on the 2nd device, and the audio will automatically switch to being from this 2nd device.  

This is how most similar products on the market do it.

 Note:

• Incoming phone calls will interrupt whatever you are doing on your PC, even if your smartphone is on silent mode. You can:

- Decline the incoming call: reject it manually on your smartphone. Once rejected, it will immediately switch back to PC;

- Answer the incoming phone call: press the phone button on the headphones to accept the call.  

- Disconnect the headphones from your phone when in an important online meeting.

• Incoming VoIP calls will NOT interrupt any activities on the device, no matter if it's from the cellphone or PC. There is no notification either. You can't use the buttons on the headphones to switch to the call.
• For older versions of the headphones, it may takes 7 seconds to switch from the PC (with the dongle) to the phone. There is a firmware upgrade which reduces it to 3 seconds here: Firmware Update for dongle (DG10)