这个句子主句tell后接双宾语you和XIAO WANG could do the job,因此主句有两种改法：
1.You were not told (by me) that XIAO WANG could do the job.
2.That XIAO WANG could do the job was not told to you (by me).注意不要忘了前面的that,整个that从句作主语,没有that就不是从句了,这样一个句子出现两套主谓是不对滴（不算从句）.
从句也可以改：
I did not tell you the job can be done by XIAO WANG.
还可以各种排列组合.感觉改从句比较自然.