My last name has a space in it. The three years that I have filed paper taxes, IRS has split up my last name into two words and put one of them as my middle nam

My last name has a space in it. The three years that I have filed paper taxes, IRS has split up my last name into two words and put one of them as my middle name. This despite the fact that I clearly label the middle name box as "n/a". I was told by the IRS representative that I should change my name.