Alt - Telephone fixture & 3 Volt Sim - Problem....

Hi,
So, I'm back among the A8 drivers... ..finally home, hehe, though....in the V8 I'm kind of, well, I don't care.

In the A8 there is an old AEG Telecar 901 and a new AEG Telecar 901. 902 built in - these should have a legendary good reception thanks to 8 Watt transmission power. So I immediately ordered an Ultracard from D2 (formerly called the twincard or something) - but the phone logs in, shows the service and the best reception strength, but when choosing it briefly and then says "please repeat" and places it on or falls into the "only emergency call possible" mode.

After a little research I have already found out that the phones need a 5 Volt Simcard, which however is no longer available, I unfortunately changed mine a few years ago and also have only 3 Volt cards.

This means in concrete terms, the phones are useless like a C-net fixed installation - except...aside from that, one here might know a solution that I haven't found on the web yet. It was ominously indicated a software update, some probably use at Ebay expensively bought old 5v prepaid cards etc. - But I'd like both phones to ring the same number.

Or has someone ev. a somewhat newer fixed installation Audi telephone retrofitted, which already with the yes from approx. 2000 delivered 3 volt cards running?

Or is it?

Weiss wer was?

Thank you and greeting,
Alex