Years ago, a hobbiest's wife suspected he was playing. She called providers, playing the role of a provider, asking for a reference. Ladies he had seen vouched for him and sometimes went beyond that - noting his generiousity and frequency.

That lead to a discussion in the community (back then Phoenix really had a community) of the whole reference system.  

Ladies, how are you handling reference calls? How do you ensure the caller is real in her reference check?

Before I respond to any reference request, I screen the provider in the same way I screen my suitors. She must have a website and/or a heavy social media presence.  

Similar incidences would occur in Atlanta where I am from so it is always best to screen everyone who contacts you to keep the community safe and discreet.

Before I answer a reference request, the lady's phone and email must match her ads/website/reviews. I almost always want to verify via email, as numbers can be spoofed. I am very careful with my client's info.