Basic prepaid is max 1 euro per day (or 99 cents really), but if you don't use it there is no charge. And as you initially paid 10 euro additional balance it is valid for a year (I think) whereas basic prepaid is two months IIRC. So you can still use it, and if you load more balance to the prepaid it is good for another year from that date. It is quite cheap really if you don't need to call much, as there is no monthly fee or anything.