Your first course of action is to complain to the surgery itself, politely but very frmly, tell them you believe that it was their incompetence that allowed your dog to gain access to his stitches and ask them what they are prepared to do about it as you would rather not take them to court but are quite prepared to do so if you don't get saisfaction. If they bluster and tell you they'll take you to court, inform them if they do that yu will counterclaim for your losses and will not be paying their bill. Vets routinely overchage, it's as if they pick and number and then treble it, however the good news is when they did something very similar to your story with my ex's cat, she did as I have suggested you do and got the bill reduced by 3/4, which under the circumstances was wholly right. If they bodged it up, didn't do as specified and made a pigs ear of it, don't pay the bill. the worse they could do is take you to county court, where you will get a chance to put your version of events and if it's found against you,pay the bill on the day and your credit record remains undamaged.