The top up form below is for those that have used all of their data before the validity end date of their data package.
For example, you used all of your data earlier than the package expiry time.
In this case you will be able to top up for more data using a "per megabyte plan"
The current rate for extra data within the validity period is € 0,15 per MB.
After your top up you can activate the "pay per megabyte plan" from this page:
http://prepaidzero.data (works only from your mobile connection)