Update of topic title: the problem is that the FP2 is killing some SIM cards. In my opinion this is another bug. A very big one.
My German Telekom SIM card is no more usable after some weeks in the Fairphone 2. FP2 and
other phones will not detect the SIM anymore. The SIM is about 8 months old and type C/W7.
There is still a discussion in the forum, i am not the only person affected. It seems
this is the same/similar bug than users of oneplus, one LG and other phones have
reported.
This is what I have understood from reading in some other forums:
The German Telekom – T-Mobile D, congster, T-Mobile A – uses some additional services on
their SIMs. The affected phones (also the FP2) are allowing this services but
could not handle it and give an error message back to the SIM. The SIM gets the
error message and starts again with asking the phone to start the services, the
phone allows it, the service tries to start, the phone can’t handle it, gives
an error message. This is an endless loop until the maximum write/reads of the
SIM are reached (4-5 weeks). For my understanding the error handling of the SIM
is buggy (endless loop), but the origin bug is on the phone (allowing SIM
services which are not executable).
As read in other forums all the SIMs from Telekom are affected (C/W2, C/W7). There is a
C/V7 which seems to keep alive longer.
There is a special SIM – C/T6 - which has solved the problem for the oneplus users.
I have to try to get such a SIM, but in the meantime my business number is dead.