There's no such thing as a student SIM.
There is such thing as a student account/plan:
I presume that you signed up as a regular user but want to change your account to avail of the student offer?
Several people have asked this before but there's nothing on the site to explain if/how this can be done.
You'll have to contact 48 support and ask them about this.
See the links in my signature below.
Why didn't you sign up as a student in the first place?
