It was Harry Potter who received a Howler from Dumbledore in *Harry Potter and the Chamber of Secrets* for using magic outside of school.
It's understandable to mix this up, as both Harry and Petunia had a contentious relationship with Dumbledore. However, Dumbledore was always supportive of Harry and even tried to explain the magical world to Petunia.
Let me know if you have any other questions about the magical world!