Freeing up Disk space

Hi all,

I have just done an offline table reorg for all tablespaces using brtools and oracle 10g, with the intention of dropping some datafiles and allocating them elsewhere.

But even though I now have 90G free I am unable to remove any datafiles.

How do I remove these datafiles or resize them properly?  I've read countless postings but none of them result in the space saving I can see in dbacockpit.

Thanks

Craig