Never call the listing agent
Never, ever call the listing agent! This is the agent on the sign outside the house. Their job is to represent the seller and get the seller the highest price and best terms. They work exclusively for the seller and you are simply a customer.
The listing agent gets paid a commission from the seller to sell their house, which they usually share 50/50 with the agent representing the buyer. Listing agents would love to represent both the seller and the buyer because they would then get 100% of the commission. Unfortunately this leaves the buyer totally unprotected while maximizing the income for the listing agent.