Phone Frustrations

I applied to a job as a mental health clinician through email yesterday with a center that works with some of the DC charter schools. To my surprise, I got a call back yesterday afternoon from them. My voicemail picked it up. However, when I tried to return the call using the number they left on the message, my cell phone immediately ended the call. There wasn't a single ring or anything..."Call Ended" would just come up on my phone every time I'd dial the number and hit send. I don't know why that would happen... anyway, I sent the guy from there another email to let him know that I've been trying to contact him. We'll see if he gets back to me.