Politely reject people

• no, i'm sorry we don't have that here
• excuse me, but you can not smoke here
• i am very sorry but you can't be here

formal and informal english

informal english:

• more personal english ( how you talk to your friends/family )
• it is more casual and spontaneous english

formal english:

• how you talk/write at work or at professional things
• you do NOT use i , we in formal english