66.Select the same edges as me and then add a new row of edges :
67.Now we will make that tiny gap between the parts of the mobile phone. Select these edges and chamfer them with a very small amount (don’t forget to check the “Open” box).
68.Now chamfer these edges too, but with a bigger amount and with a closed chamfer :
69.Now let’s go back to that tiny gap. Select the polygons which are composing the front part of the mobile phone, then detach them. After you detached these polygons hide everything except the front part.
70.Select the entire rear border and looking from the front or back, pick the scale tool, hold shift and decrease the size of the border. This will create some new polygons like below.