Locked iPhone
 

I have an odd problem with an old iPhone 4S not used for a year.

Cannot remember the passcode. Phone appears to be linked to an email address but when connecting via iTunes, the phone is not on the list of devices linked to that address - so no way of doing a factory reset via iTunes. Is there a way of totally wiping the phone so we can start again without logging into it?

Thanks

passcode
 

Just enter the wrong passcode too many times...I hear that wipes it clean.

What you describe here could be a stolen or lost phone scenario, something Apple spent a lot of time trying to avoid. I don't expect it to be easy, but try talking to Apple.

From what I recall the FBI couldn't unlock an iPhone, so good luck!

I can't personally vouch for this method (no iPhone) and note that it does a factory reset so deletes any data on the phone:

Forgot an iPhone Passcode? How to Reset the iPhone passcode | OSXDaily

I did this recently for an iphone 4 and ended up calling the apple help line (I think they called me back). They were a great help and solved the problem.
My iTunes needed updating and when this was done I was able to reset the phone.

The factory reset method noted above seems to be working. Thank you.