I stepped in the local USCIS office with my H1 paper and the company registration (name change) docs. but the officer said me you don't need to do this, when you are about to leave the country you can tell the officers about this and they will write your company new name in I-94 card.

I don't believe this.

I asked her if they have any application form for changing company name, she gave me I-129S, but it looks like sth else.

Does any one know the application form that I / my company need to file for this ??