Watch repair ruined watch

Over a month ago my husband took my Skagen watch to have the battery replaced at Jewellery by Diana. Within 5 minutes, the back of the watch had been damage after a pen knife was used to try pry open the back, and the front glass had been cracked. They were then asked to fix the watch at their own expense. The watch was returned last week with damage to the inside face of the watch. Diana denies any damage and says that the watch was designed to be this way and that I just did not notice it before. She explained that the watch was repaired out of good faith, which as much as I appreciate, is not acceptable as the watch was damaged due to negligence. The watch, which was not only expensive, bought overseas and valuable, is also of sentimental value and is now damaged beyond the point that it was when I took it into the shop. The company completely denies any responsibility.