I can't update my iphone, I get error 4000 when I update via iTunes. When I do it on the device it just freezes

Per chance are you trying to update your iPhone with it connected to a Windows computer?

Regardless, see if any of the following can help:

• How To Fix iPhone Could Not Be Updated Error 4000 in iTunes - GTU
• How to Fix 'Update Error 4000' on iPhone? - Appuals
• Error 4000 is an undocumented error code (at least publicly undocumented). It means that the connection between the phone and iTunes was interrupted in the middle of a sync or update activity. In the past this might have been caused by a flakey USB port, an antivirus or a firewall. However, there is a new cause of this error that is the result of a bug in iTunes for Windows that requires the phone not be locked during the update. -- credit: Lawrence Finch (ASC)

See this excellent user tip from contributor Lawrence Finch.

If you see Error 4000 updating your iPhon… - Apple Community

I suggest that you contact Apple Support directly then if none of the articles I provided you can help.