Embarrassed myself at the vetanarian.

I have a processing information disorder but my IQ level is normal. It has caused a lot of misunderstandings in my life. I took my puppy in for his 3rd round of shots. He’s 3 months old. They asked if I wanted preventive flea and worm prevention tablets. I said no. They did a fecal sample to check for parasites which I found odd because I didn’t ask them to do it nor did they inform me they wanted to do it. But I let that go. I checked out and drove down the road and the receipt said they had done a deworming. In my mind, i don’t know why I thought it was about the flea and worm tablets. I called and said I told the lady no and they still did it and I said they did a fecal exam without me asking for one. Apparently this is standard for all puppies I realize now that flea and worm prevention wasn’t the same thing as deworming. They gave me a $20 credit. I feel bad, how can I apologize? Should I get them a pizza and say I’m sorry for being a jerk?