Pandora usage on T-Mobile uses data, but T-Mobile has an agreement with Pandora and the customer to not charge that usage against the data allotment of the customer's line.
Verizon Wireless does have the go90 application which has some free data options, but otherwise you should look at application that allow you to download the music to your phone for off-line playback. One application that has this option is the Google Play Music application.
I'm most definitely NOT a VZW employee. If a post answered your question, please mark it as the answer.