Your friend is upset that his cell phone bills are so high. He decides to test the alternative hypothesis that the average cell phone bill for all students in your dorm was different in 2015 than it was in 2014, using $\alpha = 0.05$. He takes a random sample of $50$ students, collects their bills from both years and compares the means. He tells you that the p-value is $0.15$.
What is your interpretation?