Each MSC has slightly different rules, but.... For the most part, you call and, if the right person doesn't answer, you find a way to quickly end the conversation. Then, you try again later. You keep trying to reach the target until s/he actually answers the phone. At some point, you will be permitted to ask for the target, at which time you say that you were referred to them by somebody. You have to keep this vague as you don't want them to figure out that you are lying.
Hard work builds character and homework is good for your soul.