Material used to make this pattern:

1 Ball of crochet thread in the colour of your choice. (I have used Anchor Mercer Knitting Cotton by Coats India – Beige Color)
Steel crochet hook – Size 1.75mm.
1 Button of your choice. (I have used a wooden button)
Tapestry needle to weave in ends.
Scissor to cut off any excess thread.

Abbreviations:

Ch – chain.
Sc – single crochet.
Dc – Double crochet
Sl St – Slip stitch
st/sts – Stitch/Stitches
( ) – This bracket indicates the number of stitches in a round.

Can be easily customized to fit your mobile by increasing and decreasing the stitches and rows.