Re: SPC - anyone heard of them?
I wouldn't worry about it. If it's important, they'll write to you.
As a general rule I would never respond to security questions from anyone who has called me. If someone calls me that I have a business relationship with and I am happy to speak to them, then I call them back at a publicly available number and then go through security. It's a good way of reducing the risk of identity theft.
As for debt collectors, there is rarely a good reason for speaking to them on the phone. Always tell them to write to you. Whilst they may be monkeys on the other end of the phone they are monkeys who are trained to intimidate you. It's much easier and safer to deal with them in writing.