A REAL Shadchan or just a Shanda?

Forgive me, but I have trust issues. I mean, can you blame me? I've been cheated by the shidduch system. I've been lied to by references, shadchans, etc. about everything from a guys age, to family, to personality, to status (e.g. previously married with children). I therefore find that it's hard for me to trust anyone.
I did start off the 'naive' Bais Yaakov girl, all smiley, trusting and politely quiet on dates. Then, as time went on, and I went out on more dates, and been burned a few times, the tables sorta turned a bit. I started asking more detailed questions, I called more than a few people just to ensure the information I was given was correct. Now I have do a whole FBI internal investigation.
More than once, I received a call from an unknown woman claiming she was a shadchan and asking either to speak with me, or asking my mother about me, or asking for my resume. The first time this happened, she set me up, I went to the Big Apple to date the guy-which again, turned out to be insanely full of lies and a terrible date. I called the 'so-called' shadchan and was extremely upset about this whole sham. I asked her how she got my name and how she knew me and whose idea this whole thing really was and you know what she responded?
She said, she couldn't really tell me because it would be loshon hora.
For years, I harbored ill-will towards this woman for having the nerve/guts to call someone she didn't know and set them up with such a FAR-OFF date of a guy and then NOT EVEN TELLING ME who was behind it-which still bothers me.
But, years have gone by, and I've learned slowly to ask many more questions since then.
I've had mother's of boys who were redd to me and to whom I rejected as potentials for good reason, call me pretending to be a shadchan and asking me to email my information.
I've had friend's of boys doing the same. Heck, I've had guys themselves doing the same. But my investigative talents have proven them all unsuccessful.
The system has turned me into a bit of an untrusting freak.
So, how do I know, or how do all of you know that when someone calls you, claiming they heard about you from their friend (whom they name and who you know is a living person), and ask you for your information if they are REALLY a Shadchan or is it just a Sham?