about changing an alltel prepaid phone to a different alltel phone?

[m[Paigey]m]

i am currently a PREPAID alltel customer and i am using the lg scoop. i would like to change my phone to the lg tritan. i noticed online if i buy it the prepaid pricing is not available. could i go to a verizon store and buy this phone or is it online only? if so how could i buy the phone just so i can change it over to my prepaid service if it is possible?

simply: i have phone A, but i want phone B, how must i go about getting phone B, and keep my plan and services?