Unable to call from China

Hi everyone! Sorry my German is not good enough to explain the situation.

My current "Guthaben" for my prepaid card is about 20 euro and is still valid. I am in China now, where I can send and receive sms without any difficulty, but when I try to make a call, either to Chinese or German number, it says my number is out of service. In China the network "China Mobile"is automatically chosen, so the message "number is out of service" is in Chinese. The hotline of China Mobile could do nothing to help. What can I do? Thanks!