What do the diplomats say or do when they are summoned by the country's government they are posted in? [closed]

Suppose, a diplomat Mr. 'A' of a country 'X' is posted in another country 'Y'. Because for some reason, country X is in a diplomatically awkward position in front of Y. Say, the government of Y summons Mr. 'A' for an explanation.

What would he do or say in front of the government of Y? What is the general protocol?

I believe that he would try to calm the government of Y.

However, what if the situation is really bad?