I think you’re confusing “bandwidth” with “broadband”. Voice calls are considered low-bandwidth, since they are very “bursty”, with comparatively long periods of silence between bursts. Broadband, as may be inferred from the “broad”, uses a lot of bandwidth.
Nope, from my best understanding (and I could be wrong), voice calls do not get transmitted as "data," which we would commonly apply the term bandwidth to, but as voice on a separate faction of the carriers' networks, using different cell site equipment. For example, this means on Verizon Wireless' network, it's carried over their CDMA network. Data, on the other hand, is carried over their EVDO network (EVolution-Data Only) which is entirely separate and unaffected by voice calls.
Likewise, SMS (text messages) are carried over special channels of those networks. That's why if you're at a big event with a lot of people, such as a sporting event, your calls and data may not go through - but your text messages might (there are other reasons, such as auto-retrying, but that's another point).
That's why I mentioned Voice over LTE (VoLTE), a future technology much like Voice over IP (VoIP) to carry voice conversations over the currently data-only LTE network. Then, the carriers could shutter their legacy 2G and 3G networks and rely solely on their LTE networks (except you, Sprint).