I had this problem when I first switched to sprint, and I'm surprised to see such little available information on this topic as I have thoroughly researched this topic time to time.
I switched to sprint to save money, I bought the new M9 and was very excited to have unlimited data. I added hotspot to use on my laptop for work because in my warehouse I do not have direct internet lines in my makeshift office. After realizing my internet broke up every time I received a call I was furious to find out most of the new Sprint phones no longer have dual antenna's or radios..BULL****. Determined to find a way... I stumbled upon my gf's phone by accident, she could have voice and data simultaneously on her samsung galaxy s4 model 720. Now there's two model 720 models you need make sure you get the right one with dual radios. So inevitably I traded in my M9 for a S4, but now I'm rooted with hotspot and big middle finger to sprint and unlimited data. The s4 is so good with hotspot I watch HD netflix, and dont have a internet bill!