I've worked with them a lot but haven't gotten through in a few recent attempts.

I found verification difficult and actually impossible

I can not help that your references never responded, one was out of town for the summer and the other did not get back to me:  we do work verification also, I'm assuming that was not the route you wanted to go..... So, I'm sorry that I could not verify you.  I do not like to rely on references I like doing my own screening.   Thanks and sorry!  

I'll try calling you in person next time. I've made it work with others.

So how do you "do your own verification?"
All I was asked for were references?
Others accepted linked in or phone chat.  
Just curious.