Are you trying to root it (install su in the /system/bin folder so you can run rooted apps) or unlock it (use it on other carriers)?
One has nothing to do with the other.
If you want to root it, try
Towel Root. (Kingo should have rooted it also.)
If you want to unlock it, they were correct - you give them the IMEI of the phone (*#06# on the dialer) and, for a price, they'll give you the unlock code. You then put in the other SIM card (when the phone is turned off) and when you turn it on, it'll ask you for the unlock code. Put it in (carefully - you have a limited number of tries - if the first one doesn't work, don't keep trying it, contact the company again) and the phone will accept any SIM. (That doesn't mean it'll work with any carrier [it looks like a TMobile phone so you may only get 3G data on another carrier]).