What to do if you lost your phone?
You should immediately lock your SIM card. To do so you have to contact your provider either online or by phone.
Update: Jan 2014
Most providers offer a function on their website where you can lock your card easily. You can also call your provider or even call the general locking line. This service will forward you directly to your provider.
In order to lock your SIM card you need either the number of your SIM card, your customer ID or your customer password. When on the phone with your provider, you can immediately order a new SIM card. But your provider will charge you for it. Please check the particular conditions of your provider.
Locking emergency (mobile phone, credit card): 116 116