I got mine just a month ago. The Bluetooth pairing with phone worked without a problem.
Then, out of the blue (excuse the pun) the Bluetooth stopped working. The blue LED on the headset controller would not come on, regardless how long or short I pressed the Bluetooth button.
The local reseller opened the battery pack, took out one battery and flicked the two micro switches in the battery compartment (for "AutoOff", and for "Mono/Stereo") back and forth. Then he put back the battery and - voila - everything was working again!
While this is not documented anywhere in the 'trouble shooting' section of the A20 manual, this procedure seem to work like a reboot for dreaded Microsoft computers. It may well be the taking out of the batteries in itself that did a 'soft reset' - not sure what toggling of switches can help with no power source present. But then again, I don't really understand how these things work.