还有一件事 怎么说？

There's another thing.

By the way,....
Plus,....
Another thing is ...

还有一件事
One more thing. / Just one more thing.

By the way 最常用

Another thing is ...

And one more thing ... 也可以

one more thing,
moreover

1)another thing ;
2)one more thing;
3)in addition ;
4)besides;