How do I connect to the Internet using the UMTS PC-Card Option Globetrotter 3G+ and Linux?

This set of instructions should work also for all other UMTS PC-Cards that are auto-detected by the flavour of Linux that you have. And it works also for HSDPA cards (like the Option GT 3G+ actually is) and probably also for pure GPRS / EDGE cards.
Configure the SIM card with a mobile phone so that the PIN is not asked for before registering into the mobile network. You can later let it be asked for, and if you want, configure the answer in a PPP chatscript, but for now this is the easiest variant. If we don’t have to enter the PIN, the card cannot get locked just because of technical problems when transmitting the PIN.
Insert the SIM card into the UMTS card. Insert the UMTS card in your notebook.
If you have external speakers on, and if these are sensitive to mobile phone waves, you should hear the card registering into the network.
Check if /dev/noz0 to /dev/noz4 is there. The names may vary for your card model.
Start kppp as your normal user.
In kppp, create a new modem for device /dev/noz0.
In kppp, create a new account. Phone number: *99***1#. Default values for the rest (i.e. authentication PAP/CHAP, dynamic IP address, standard gateway, automatic DNS, no login script). The dial-in phone number is the same for all mobile network carriers in Germany, independent of the UMTS card that you use.
For user name and password, choose anything you like. There’s no authentication expected on the side of the mobile carrier because, seemingly, having the SIM card is authentication enough. This is valid for prepaid mobile phone contracts, and at least some postpaid contracts (here, for the O2 Genion Card-S online).
In kppp, click connect. After it connected, it will minimize into the KDE toolbar. Then, try a “ping google.de” or try surfing.
I myself used the following to choose the Option GT 3G+ card as one that works at linux, and for configuring it: http://www.linux-user.de/ausgabe/2007/10/072-umts/index.html
If you’re looking for a chesp volume package for UMTS Internet traffic: in Germany, try Simyo “Internetpaket 1GB”, see http://www.simyo.de/de/informieren/aktuell/handy-internetpaket1gb.html .