This is my first bluetooth and I'm having a problem getting my Jabra BT125 into discovery mode

Turn the Bluetooth on and hold down the button until the light is solid blue Put the phone in discovery mode or search for a Bluetooth device Pair the Bluetooth to the phone and enter the pass code "0000"

No, bluetooth means compatible.
Have you set your headset to discovery mode before you looked for it with your phone? I think you hold down the main button until the light stays lit.

taken from the manual found at

http://www.jabra.com/sites/Jabra/GNimages/Products/WirelessHeadset/BT125%20Black/Documents/User%20manual/BT125_UM_NA_EN_471.pdf

1. Put the headset in pairing mode
• Make sure the headset is off .
• Press and hold the answer/end button until a solid blue light comes on.

2. Set your Bluetooth phone to ‘discover’ the Jabra BT125
Follow your phone’s instruction guide. This usually involves going to a ‘setup,’ ‘connect’ or ‘Bluetooth’ menu on your phone and selecting the option to ‘discover’ or ‘add’ a Bluetooth device.* (See example from a typical mobile phone in fig. 3).

3. Your phone will find the Jabra BT125
Your phone then asks if you want to pair with it. Accept by pressing ‘Yes’ or ‘OK’ on the phone and confirm with the passkey or PIN = 0000 (4 zeros). Your phone will confirm when pairing is complete. In case of unsuccessful pairing, repeat steps 1 to 3.

Hold down the power button until it becomes a steady blue light. This should put it in discovery mode

you have to switch the bluetooth headset to pairing mode not just swithcing it on. Hold the power on button continuously even after it switches on then the light will remain on. Then you switch on the bluetooth in the mobile and start searching for bluetooth devices. You will find your bluetooth headset in the mobile. Select it and pair. Usual code will be 0000, but it might differ check with the manual which can be found online too. This will definitely solve your problem.

Turn on your BT125 by presiing button for 4-5 secs
in ur dopod go to settings>communication>blutooth
In the mode tab:check on > turn on bluetooth and >make device visible to others
Then go to devices tab: click on add new devices, your dopod will start searching nereby bluetooth devices...during this time press the button on your BT125 for about 2 secs, it will try to connect to dopod and a message will be displayed : "BT125 wants to connects......" say yes ...it will ask for the passkey enetr 0000 and there you go ...tada

Make sure the Jabra headset is set to pairing mode, otherwise the phone cannot find the headset. The manual should have instructions to set the headset in pairing mode. While the headset is in pairing mode, have the G1 search for the headset (Settings > Wireless Controls > Bluetooth Settings). When it finds the headset select it and type 0000 for the PIN code.

check the bluetooth is in visible mode or not

SET YOUR BT125 JABRA  in pairing mode then try to seek in mobile 
or reset your mobile 

I had the same problem trying to connect my old Jabra BT125 headset to my brothers PS3, here's what worked for me:

-Turn on the headset by holding down the button but keeping it down until a solid light comes on.

This puts the headset into discovery mode, you can the start scanning for the device and it should find it.