I have an iphone 6 that is locked with a passcode, i have tried to unlock it using the apple instructions but it still isn't working

If you’ve followed the complete instructions including receiving feedback indicating that iTunes has recognized and connected to and is resetting the device, and without a successful device reset, contact Apple (Get Support) and discuss your options and alternatives.

What instructions are those?

Do you mean this: If you forgot the passcode for your iPhone, iPad, or iPod touch, or your device is disabled

If so, what happens when you go through that process?