unlimited data extension for post paid customer

Hallo,

I use 10 GB post paid plan with o2, which has option to extend the data usage, for example unlimited dat plan for one month. However when I try to book the unlimited plan, mein o2 app throws error. It would be great if you can help me fixing this issue and I would able to extend my data.

Edit by o2_Steffen: Thread moved from Mein o2 to English: Mobile