PMI Drops off after 78% LTV??

[Neil Blalock]

Hi BP community, I was hoping to get the answer here for this question. My lender has approved me for my loan and said I can do 15% down instead of 20% and the PMI will drop automatically after 78% LTV. My dad who has bought multiple properties says PMI does not drop unless you do a refi on the property after having enough equity in it. Thanks for the help.