I'm not aware of any speech-to-ASL software. And unfortunately, I'd be willing to bet there would be two big problems with speech-to-text software.
First is getting the software to recognize the audio from a phone call. Most of the programs that I've worked with are designed to take audio input from a mic in jack and not much else. Meaning that even if you were to run the call through the computer instead of a phone line (say via skype) the programs can't intercept the audio and translate it into text.
Second, their accuracy typically is poor to middlin' until you "train" the program to recognize how you speak. Given that you want it recognize an "unknown" voice each time it's accuracy wouldn't be high enough that I'd trust it for something like job search info.
There's a reason why VRS and regular relay are still used. They work.