Facing a barrage of calls from agents wanting to list your property is something you need to be prepared for. They are only doing their job so don't get too annoyed or upset. Besides they are use to knock-backs and in most cases immune to abuse. Just be polite and tell them you are handling the sale yourself.
They may even offer some tips and guidance.
Be prepared for the oldest trick in the bookSome agents will ring telling you they have a buyer. Don't slam down the phone too quickly, because they might be telling the truth. They might genuinely have a buyer for your house. What they usually mean is that they have buyers who are looking to buy a house in your area. Not necessarily your house, but "a" house in your area. There is a big difference!
They may even ask, "Is it alright if I bring someone around to have a look? "
Again that doesn't necessarily mean that they have a buyer for your home. Remember, they are in the business of showing people through houses.
Most agents will just be fishing for a listing. They just want to get their foot in the door so they can pitch for your commission.
If you do want to sell your house yourself then just tell the truth.
If they persist then suggest they post you some information. They probably won't bother.