Grice’s maxim of relevance states that:

“expect a partner’s contribution to be appropriate to immediate needs at each stage of the transaction”.Leech (1983: 94)

In the following turns, we see in line 01 that A signals to B that he has identified her. However, B ignores this. This breaks the maxim of relevance. 

A 01 ‘You must be Julie,’ I said.            
B 02 'Can I help you?'

B breaks the maxim of relevance by flouting it. This signals to A an implicature. The implicature is: first tell me what you want before I identify myself.

This might signal to some extent B’s status within the conversation. She has the right to demand what the other person wants before she will let the conversation go forward.

References

Leech, G. (1983). Principles of Pragmatics. London: Longman