Basically trying to find out if there was a change in hours of use of phone, and if this change has something to do with attachment levels.
So at last we know what you actually want to find out.
The simplest way would be a calculation of the individual differences
hours after - hours before.
You can correlate this differences with attachment, using Spearman's rank correlation. This
will tell you whether there is an association between attachment and behavior change.
For interpretation, you should additionally check whether hours of phone use at baseline was
closely associated with attachment (Spearman correlation). Possibly, those with high attachment
were already using their phone extremely often, so that this could not increase much more
(ceiling effect).
With kind regards
Karabiner