im trying to buy a locked sidekick but i dont know if locked means i cant add a sim card by cingular wireless or if it means i cant use a sim card even by tmobile unless i bought the sidekick from terh store myself?

cause im not trying to use a cingular sim card with the phone, im trying to buy a tmobile plan and use that newly activated sim card.

so what does having a locked phone mean?

im hoping it jsut means that i cant use a sim card from a different company, not that i cant use a new activated sim card taht didnt come with the phone.