Are you still connecting the BB to your work computer and receiving corporate email? The restrictions will apply to all devices that are connected to your company's BES (blackberry enterprise server) regardless whether the device is yours or the company's and regardless who pays the bill data service. If you want company email on your device, you're stuck with the company's limitations.
If, on the other hand, you simply want to use the device on your own and not connect to your company's BES, ask your company to push a blank IT policy to your device or follow the instructions here: Remove I.T. Policy from a BlackBerry... - BlackBerry Forums at CrackBerry.com
But, be forewarned that following the instructions, and then reattaching the device to the company's BES will cause the restrictions to be pushed down again. Plus, many people here claim that it's grounds for termination (it's not at my firm, but that's just my limited experience).