telling about a situation in the past?

[foreigner]

Hi Guys:

I am trying to write a letter to explain a situation about what happened between a person "X" and me in the past. The situation is like this:

I signed a contract, then X asked me to do additional job after that (both actions are in the past)

Now, I am trying to explain this situation by the following sentence, which I am not sure wether correct or can be improved. The sentence is:

When X asked me to do the job, I was already signed and submitted the contract.

Can you guys give me any suggestions

Thanks heaps!

[Mariner]

"I signed a contract, then X asked me to do [some] additional job (after that)"
>
>
"When X asked me to do the job, I had already signed and submitted the contract"