Student or Learner
Why in the above sentence "a" is used before Mr. Davis? I wouldn't use anything.
It's a short way of saying '...a man named Mr Davis called.'
Anna, for the second time in two days, there is no need to write a new post to say thank you. Simply click the Like button on any posts you find helpful. It means that we don't have to open the thread again to read your new post and then find that it doesn't include any new information or an additional question.