DualSim I-42 with Vodacom Southafrica

I wanted to use my iPhone4s with a german T-Mobile Simcard (SIM1)
and a Southafrica Vodacom prepaid (64k) card (SIM2), Roaming is activated.

I have installed the I-42 adapter and the phone is showing SIM1 in the display.

But it does not work, neither in Germany nor in Southafrica.
It does not switch from SIM1 to SIM2.
Only network in with SIM1 is connected but when I try to activate SIM2 then the network is disconnected and I do not have any conenction on both SIM cards. (in germany it switched back to SIM1 after a while)

I have not tried using two german T-Mobile cards yet.

Anybody who can help?

please check the following.
Your sim cards may be too old
Also please disable sim pin codes.