In order to pair it with your phone, it must be in pairing mode first. If it has never been paired to another device before, just by opening the boom, the indicator light should flash alternately in red and blue, thus indicating it is in pairing mode. Otherwise, to force it to go into pairing mode, press and hold the volume (either + or -) whist opening the boom. It should flash alternately in red and blue. Only then, make the other device's b'luetooth application search for new devices. After a while, the VMX100 should appear on-screen. Select it and make it connect. If a pairing code (or PIN, or passkey) is requested, enter '0000' (four zeros). If the pairing process is successful. Now, ot pair it with the other device (the VMX100 is able to pair to up to 4 different devices), make sure the previous device has its bluetooth radio turned off. Then, repeat the pairing process with the other device.
Hope you are able to sort your problems out soon.

By the way, if your headset's user guide happens to be missing, feel free to download it from this location.

Regards, Carlos