why does wemmick give advice at walworth that contradicts with what he said on gerrad street? Great expectations. Chapter 36-37.

From the text:

"Mr. Pip," he replied, with gravity, "Walworth is one place, and this office is another. Much as the Aged is one person, and Mr. Jaggers is another. They must not be confounded together. My Walworth sentiments must be taken at Walworth; none but my official sentiments can be taken in this office."