German Fonic questions...

[inquisitor]

Generally registration of SIM cards is a legal requirement in Germany as in most European countries and most operators will ask you for your ID card when you buy a SIM.

However Fonic SIMs are not being registered by the personnel if you buy one in a shop, but you have to provide your personal details yourself either online or - if registered by paper - on the form that comes with the SIM card. Also Fonic do not require any proof of identity upon activation.

I believe the fact that they require an ID card for an ownership change is just a security measure to deter people from changing ownership without the original owner's approval.
But be aware that the change of ownership is subject to a charge of € 10 (see p.2 "Besitzerwechsel" of http://www.fonic.de/html/pdf/FONIC_T...Preisliste.pdf).
I wouldn't change the ownership if I were you.

Originally Posted by Kritiker

What difficulties are there in leaving the ownership data as is, assuming the previous owner doesn't care?

The only disadvantages of not changing the personal details are that you won't be able to request a new SIM card (with the old number) if you lose your's and you won't be able to export your number to another operator.

All I really need, AFAIK, is to change the caller-id that is displayed when I call people?

First of all you can't change the callerID, but you can only disable it so no number would be presented to the called party. But why do you want to change the callerID? If the SIM card is your's, why shouldn't people see your number and so be able to call you back?