Prepaid mobile phone package for Frankfurt, Germany

Lebara's website is available completely in English, as it's marketed to immigrants and offers cheap international calls. The national and data plans are more expensive than those offered by other discount providers like Simyo, Blau and Fonic, but still reasonable.

However, they will deliver the SIM card only to German residential addresses. I doubt whether you can find any alternative that does not require this, since it's mandated by German law that all SIM cards must be registered with the buyer's address.

On most German supermarkets you can alredy by a Prepaid-SIM card. There are also offers with access to internet avaialble. I really recommend to try to translate the German webpages. E.g. http://www.alditalk.de/sued/ in such cases.

It all depends on your needs and how long will you need the SIM card. If you intend to throw the card away after your stay, it pretty much doesn't matter which provider you choose, they are quite close price-wise on prepaid cards.

If you want to keep the card for re-use on later visits to Germany, then it may be important to check how long the SIM card remains valid without being recharged.

There are differences among carriers regarding the network coverage. In cities they're all good, but if you will be travelling to rural areas, this may be important. Generally, T-Mobile and Vodafone have the best and broadest coverage. The other two carriers (O2 and E-Plus) recently merged, so maybe they have caught up on that, but not sure.

Lebara is the best option if you intend to make international calls while in Germany, for example back home. They're unbeatable for int'l calls, especially to Europe and USA. If you need something for national German calls, get another carrier. Lebara is relatively expensive on national calls. Ironically, most of their internatonal rates are cheaper than the national rate. They're using the T-Mobile network and have stable coverage.

Whether you should get the card on-site, or order it online beforehand, depends on your time of arrival. During the day it will probably be less of a hassle to buy in at the airport from some supermarket or kiosk. Newspaper shops should also have such stuff available. If you're arriving late at night, you may be out of luck. In that case, if I were you, I'd let my sister buy the card up front, and then just live with the roaming charges if I have to call her before I get the card.