Just send an email terminating the relationship. CC the broker. Move on. This isn't that big a deal.
The best way to tell your realtor you are no longer interested in working with them is to talk to them directly. Buyers or sellers may have a slightly different process on ending the relationship in the most respectful way possible.
Six things buyers should never do when dealing with an estate... DON'T give them your real email address. DON'T bother speaking to their recommended mortgage broker. DON'T use their recommended conveyancing service. DON'T downplay your budget. DON'T accept what they say about other interest or offers they have received.
Anything about property or negotiations. Because this is not their area of expertise. Don't ask themMoreAnything about property or negotiations. Because this is not their area of expertise. Don't ask them whether you should buy a brand new apartment or a house and land package.