You assume too much intelligence and benevolence among Sprint sales staff. Yes, here at S4GRU, we have some great front line sales and tech support Sprint staffers -- they are knowledgeable about and interested in what they do. But they are the exception rather than the rule. Like it or not, most wireless front line staff seem not the sharpest tools in the shed and/or disinterested in their jobs.
Now, combine that employee lassitude with consumer ignorance, and you have got a real challenge. Honestly, most consumers are stupid about most things. What percentage do you think already understand or could quickly comprehend why simultaneous voice works when on a Wi-Fi or WiMAX data connection but not on a CDMA2000 or LTE connection?
Therein lie several problems with your "selling point"...
AJ