A: Hi, [P]rofessor Anderson.. wondering if you had a couple of minutes...
B: Of course[,] Paula.
...from a TOEFL [textbook]
Indeed, if Paula was talking to Professor Anderson there and then, then the present tense should be used (i.e. I am wondering if you have a couple of minutes.)
I am hoping that you can supply additional context. I am wondering if Paula was referring to an incident in the past when the professor could have had a few minutes to spare?
Example: Hi Professor Anderson, I am wondering if you had a couple of minutes last week to look through my proposal?
So, I would say that it could be right or wrong, depending on what the context is.
I hope this helps.