Why has my Lumia 535 switched to demo mode and how do I change it back?

[WPCentral Question]

My Lumia 535 switched over to demo mode, I've had it for months and suddenly my contacts, text etc have gone. All the help forums say it shouldn't have been sold if it was a demo model but it wasn't until two days ago.

 

[charlatan1978]

Hi, as you have seen in other forums demo models are not supposed to be sold to customers.
If you have only had the phone a matter of months I would take it back to where you purchased it from.