Why are you trying to do this on a phone at all?? I'm sure you have a PC with a speaker, microphone and internet connection. Click the link on a PC and you don't need the phone to be involved at all. For free, without having to register or give credit card details.
McBryce.
No there are no mic or camera on my computer, otherwise I would as you say just use that, rather than trying to get it working on a bloody smartphone !
It's a desktop computer not a modern laptop which have mic and camera as standard since these days laptops are basically closer to a glorified smartphone than an actual computer.
I don't have a mic or webcam on my desktop either, they can be hacked and as far I'm concerned, they are a security risk. I do have a mic that I can plug in if required, one which I had to buy in order to conduct a online meeting with someone from RS when I was pissed with them. I sent off my HP3478A for calibration to them, and a couple of weeks later they claimed they couldn't do it and retuned it to me and offered a discount against a new meter. Strange how they couldn't calibrate it, but I managed to do it myself in the end without all of their fancy gear.
Anyway, I do have a laptop as well, and I have taped up the webcam on that and disabled the mic so good luck any hackers getting access to that, especially as it sits under my bench most of the time not used.
Good luck with the interview. Fingers crossed for you.