Up front: I have been a client for 3 years, buying regularly, with no bad experiences.
(check their site at https:// www.bulliondirect.com)
You can buy via their Catalog, most times paying retail. Although a fast market in either direction would refresh the catalog prices faster then the Nucleo exchange (see below) where independent people like you and I can transact.
The service I like is called the Nucleo exchange. Here you buy & sell like a market, dealing with others with Bullion Direct as the "broker." You can access the bid/ask prices of many different forms of bullion that the majority of us tend to purchase. The exchange displays the depth of buyers and sellers at the various prices and the volume available at each price. As a buyer, you can pay what the lowest seller is offering to sell at (ask) or you can enter a bid to buy at a lower price for when the market moves lower or a seller wants to quickly sell metal they will accept your bid. The reverse is true for sellers. BD charges a 1% transaction fee to both sides of the transaction.
Although I won't further detail the Nucleo process, suffice to say that I have bought or sold hundreds of ounces of silver & gold as a customer.
The company is located in Austin, TX. Shipping is reliable, usually about a week. Customer service is friendly and reliable to provide quick answers. The whole market exchange (Nucleo) process is unique and is typically the most efficient in terms of price. I check about a dozen sites daily and have found that buying from fellow PMers to be by far about the cheapest. Every item I have bought I received as uncirculated and packaged extremely well.