Variants when adding a service product

Site URL: https://www.beatdrop.ca/beat-drop-single-course

Hi,

How would I be able to create our service product form so that when someone chooses a certain class, that the corresponding date(s) will appear under our "Start Date" section? All of our class dates show up in our Start Date dropdown and it gets quite confusing. I've attached screenshots. 

i.e. If I choose DJ101 and I only want to see the dates we've set up for this class and not all dates for every class we have on the form.