What would be the cheapest train ticket for this area (Düsseldorf)?

I'll be in Germany (Düsseldorf) soon, and public transport tickets are so complicated. The two of us want to explore the lower area in one afternoon. We only need three rides of about 30 minutes spread throughout the afternoon. Does anyone know the cheapest way to do this? The best I found was a 24-hour…

Rheinbahn is already debiting the ticket even though it hasn't even arrived yet?

I took out a subscription for Ticket 1000 starting September 1st, 2022, in the middle of last month. The ticket still hasn't arrived, but today the full €101.99 was debited. I called and just got a voicemail saying that there might be delays due to high demand and that I should refrain from inquiring about…