That is an excellent question. In the absence of any specific instructions from you to your agent, an agent does NOT have any duty or obligation to present offers once you have accepted and signed a contract. However, if you have instructed your agent to continue presenting offers, then he must follow your instructions. If he has not followed your instructions, he or she may be in violation of NAR's Code of Ethics as well as Arizona statute.
A good agent will always marketing a property, even when under contract, and will encourage submission of backup offers.