So if I'm not traveling I stay with the cheapest data option for my occasionally otg stuff and on heavy travel months I choose larger packages, because I found myself using more often, for example as access point to notebook.
I also have an Kaufland (Telekom) Prepaid card, that said it would provide basic, very slow internet, for free so that text messages over chat works, bur I don't know if I got the wrong APN settings, it has problems in my second slot or it only works if you top it up regularly, but that internet and rest never really worked, even the account management over the website doesn't really work for me.