If you subscribe to any DIGI internet plan, you will notice it will automatically renew your packages until you are out of credit, and you reload it will deduct your credit again to renew the package. Here is the trick how to stop DIGI internet plan (daily, weekly and monthly plan) for any DIGI prepaid Internet plan:
1. Dial " *116*1#
2. Now select your subscribed Internet plan.
For example press 2 if you are subscribed to weekly RM5.
3. Now press 1 to unsubscribe and then press 1 again for confirmation.
Finally DIGI will send you an SMS saying that your subscription has ended. Now your prepaid credit is safe =)