Torn pant worn once

I bought pants on the 6th December then wore them on the 16th. I washed the pants once, and when I was looking forward to wearing them again, one leg of the pant looks like when a pantihose has ran. We went to the shop and showed them , the lady I think she's a manager, stated she will send an email and left us like that. We had to give her our contact number as she looked uninterested and didn't bother asking for details