Fast talkers, dialect, no time to think it through. That's not the German you learned. Tell me who to call and what it's about, in English or German, and I'll make the call for you, in German.
On the phone, every pause is obvious, and the other person talks faster than you can ask them to slow down. In a chat you have time. On a call you don't. So don't make the call yourself. I won't ask why. I'll just call.
The call won't get easier if it sits another week. Just send it over.