I have never heard of access to "Settings" being disabled unless the device is through a company (you don't own it), it has a parental lock on it or it has a virus/malware.
If it is one of the first two, then there is nothing you can do about it. You would have to get the company or the parent to allow access (depending on which one it is). If it is neither of these then I suggest checking the device for viruses.