Paid but no work done

I got my jeans back a few weeks ago but I noticed they were still long. I came back and mentioned the problem. They told me that they were not the ones who worked on my jeans and the jeans I'm showing is still factory stitched! I was surprised by this.

That would mean that I paid for my jeans, got it back and yet no work was done on it.

They refuse to believe my side of the story and they wouldn't listen.

I will not go through all that trouble for a service costing less than $7 if I really did not have my jeans cut (supposedly!) with them.