Buying a BlackBerry off eBay - BlackBerryFAQ
Read that.^^
If your carrier is TMo here in the US, you will need to purchase their International calling plan and International BlackBerry Data Plan.
There are other options as well (using a local SIM from the country you are in, getting a data plan there, etc.), but honestly, none of those options will easy nor cheap.
You really can't "remove" an IT Policy, you can replace it with a blank one. Be very careful buying a used BB off eBay for a trip coming up shortly.