Track the edge of the phone and the tracking markers only, making sure to go a few pixels outside the edges, and avoid the reflection entirely. This will be a complicated shape that probably uses the add to x spline tool to get it right. Track from the end of the shot to the beginning, because you always want to track from the largest in frame area that is most parallel to the camera and least blurry. Use adjust track to correct any drift.
Honestly, I hate using tracking markers because of the problem of having to remove them. You can try the remove tool with interpolation on to try and get this correct looking but you might be better off replacing the reflection entirely.
Resolution and lack of compression are vital for a good track, because Mocha is a texture tracker. Anything you can do to preserve texture is a good thing. Anything that blows texture away (compression, low resolution, time remapping) is going to give you limited results.
Hope that helps, you should be able to track this shot but it’s a mid-range of difficulty.