Answer: Hassan could speak with the broker and possibly come to a mutual agreement that it is in both parties' best interest to cancel the listing.
Explanation:
If Hassan feels unhappy with the broker´s work, he can request to cancel the agreement, especially if he can firmly explain the reason´s he has. Most brokers rather avoid dealing with an unhappy client, and will probably have no issue with the cancelation.
However, if Hassan plans to re-list with a different Realtor, requesting an Unconditional Release is recommendable.