Yet another question. I see how I can purchase top-ups with credit cards and paypal here:
Prepaid-Karte & Handy aufladen – Prepaid online aufladen bei Cabox.de
If I regardless of whether I top-up with a O2 or Tchibo voucher, with I decide to use it on the O2 SIM, I will be purchasing a plan at the O2 rate (for example the XL data pak,25 Euros/mon flatrate). If I had the Tchibo SIM, I could topup and later purchase the same data pack at 20 Euros/mon. Is that right?
I originally thought I could top-up the O2 SIM with a Tchibo voucher and then purchase the XL pak at the Tchibo (20 Euro) rate. Upon reflection, it seems top-ups do not control the price for the data plan.