If the phone you have isn't on their list you have to call.
In general, as a baseline for voice you need a CDMA compatible, Sprint branded phone which includes the 1900MHz PCS frequency band. AFAIK, for updated data reception you would want to include Sprint compatible LTE frequency bands too, including their latest 2.5GHz band. See here:
https://en.wikipedia.org/wiki/Sprint_Corporation#Wireless_networks

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