Noc for using same name of existing company

Hi,

I have a proprietorship firm for IT. I want to register it as LLP. but the name is already registered by my my friend. As per legal advice I need a NOC only which will let my company use the same name. My question is. will this NOC is just a writing from the Owner of that company? or it should be on a stamp paper and notarised .

How sould I make this NOC.