How much will it cost to change your plan to the sidekick plan from a samsung gravity?

i got a samsung gravity and my sister gave me her sidekick 08 , and she said my internet might cost to much and she didnt tell me how much it would cost so can someone tell me how much the internet will cost if i change it, and how much would it cost to change the plan to the data sidekick 08 plan...please respondHow much will it cost to change your plan to the sidekick plan from a samsung gravity?I think it's $35 for the data plan along w/ a voice plan.