I had similar issues with the BH-503 and found a working hard reset method. Here's the detailed process:

1. Start with the headset completely powered off
2. Press and hold both the Power button and Volume Up button simultaneously for about 10 seconds
3. The LED should flash red and blue alternatively
4. Release both buttons when you see this pattern
5. The headset will power off automatically
6. Power it back on normally - it should now be reset to factory settings

This will clear all paired device information and restore default settings. If this doesn't work on your first try, make sure the headset has sufficient charge - low battery can prevent proper reset.

After resetting, you'll need to:

• Put the headset in pairing mode (press power button for 5 seconds until LED flashes blue/red)
• Re-pair with your devices
• Reconfigure any custom settings

Note: This model is quite old now (released 2008), so if you're having persistent issues even after reset, it might be worth considering an upgrade. Battery life tends to degrade significantly on these older Bluetooth headsets.

For reference, the original default settings were:

• Volume level: Medium
• Auto-answer: Off
• Last number redial: Enabled
• Multipoint connection: Enabled

If the reset doesn't resolve your specific issue, please share what problem you're experiencing - there might be alternative solutions to try.

Can confirm

Unfortunately, the BH-503 doesn\'t have a documented hard reset procedure. Try turning it off, then pressing and holding the power button for 10-15 seconds. If that doesn\'t work, consult Nokia support.