Solved! Changing settings as marshamallow

You cannot upgrade to another version of the OS unless that option is showing as an update within your phone's "Settings". If there is no update/upgrade listed there, then your device is not able to be upgraded to a new version of Android.

Your only other options are to root that device (which I would not recommend for any device as it is very risky and can easily brick the device) or to get a newer device.