From the movie Nappily Ever After:
[Violet's mom is straightening her daughter's hair with a hot comb.]
Violet: It seems like we've been preparing for this moment forever.
Violet's Mom: I told you one day your prince would come. So, does Clint still think the party's a surprise?
Violet: He has been calling my office, asking April for help...so I have been able to plan everything.
(For context: Clint is Violet's boyfriend, and April is her assistant. Violet found a box in Clint's pocket, and thinks that he is going to propose to her at her birthday night.)
I don't understand the use of present perfect in the bold parts. Doesn't past simple work here?