how to apply for previous promotion later

hii I mailed for my pramotion letter of assistant manager but they provide me my recent promotion sr assistant manager latter and told me they didn't have my assistance manager pramotion letter so what I have to do for my assistance manager pramotion letter.. i required it urgently why they are not able to provide me this and where I have to talk for this

Hi,

I assume you are referring to Promotion letter.

To whom you had emailed ? to your HR of current employer or past employer ?

If you had been promoted as Assistant Manager then you should be having promotion letter issued to you isn't it ?

Please post question with all information to get right suggestion.

You have to follow up with your HR Department for getting a copy of the promotion order as Assistant Manager. If not HR, may be Finance could help. If a copy was endorsed to him, the departmental head could be in a position to help.
The order promoting as Sr Assistant Manager would be indicating you as Assistant Manager. So also, when you are already promoted as Sr Assistant Manager, it is evident that you have been promoted as Assistant Manager.