Are you on a corporate BES? The IT Policy can be removed, however, if on a BES your corporate employer must have directed that your device retain this IT Policy in order to be on their network.
What BES is it on? If you only want BIS service, just subscribe to via your Tmobile carrier.
Then remove the IT Policy per the FAQ here: Remove IT Policy - BlackBerryFAQ
But, you need to remove the device from the BES first as it will push the IT Policy back to the BB again and again.