According to
a blog entry on their website Fonic offers free replacement of newly bought SIM cards with Nano SIMs but I guess there are still plenty of old SIM cards on shop shelves. So better print out
this template and take a pair of sharp scissors with you (but don't carry them in your hand luggage). By the way Fonic also offers a SIM card with even better tariffs under the brand of "Lidl mobile".