IS IT ABBU ( DAD) OR ABU AS COKE SAYS

Coke or Coca-Cola has come up with the idea of advertising coke by putting names of family members or people close to your heart in local languages.
In Pakistan, where Urdu is the national language - MOST but not all words have been borrowed from Urdu.
One such word is abbu which means father and coke has spelled it as ' ABU' - this romanization of the word dad or father is  absolutely WRONG. It should be ABBU and not abu.
In negligence they are teaching kids all sort of wrong spellings even if its the romanization.