Sell a bill of goods is an idiomatic phrase that means to deceive or trick someone into believing something that is false. The antonyms for this expression can include honest, truthful, sincere, genuine, and credible. Instead of deceiving someone, one should be honest and forthcoming with information. For instance, if one is selling a product, they should not mislead customers with false information or overpraising the product's features. Instead, they should provide factual information, let the customer make their own decision, and ensure the product meets the customer's expectations. In conclusion, when dealing with customers or clients, honesty is always the best policy.