Siri not recognizing custom phone names

I have used custom phone names on all my contacts (Work 1, Mobile 2, etc.) to accommodate for multiple phones under each category. With voice dialing, I could say, "Call Smith, Bob and Mary, mobile 2" and with 100% accuracy, my iphone would place the call. Now with Siri, voice dialing has become usable. The closest I have gotten to making a successful call is by saying, "I want to call the mobile 2 phone number of Bob and Mary Smith." Siri will answer back "Which phone number for Smith, Bob and Mary . . . Home, Work 1, Work 2, Mobile 1, Mobile 2" I'll say, "Mobile 2" and Siri will respond, "There is no mobile number found for Smith, Bob and Mary."

All that to say voice dialing has become completely useless now that I'm using Siri. Perhaps I need to speak in a different way. Any thoughts?

Steve