What is Crosscheck?

Crosscheck is to make certain that information, a calculation, etc. Is it correct, by asking a different person or using a different method of calculation.

Let's have a real life example, I have a deal with a Company and the owner is somehow close to me so i thought let's have all the info from Company Hotline at first and then have confirmation with the Owner. So I called the company's Hotline number and gathered my needed information. And then called the owner to close the deal and I got the surprise at that point. One product which was rated 5$ by the info of the hotline number became 10$ & the owner telling me that he's giving me a 50% discount.

So here one good practice that helps me is Crosscheck. And one bad practice that makes the owner caught is not maintaining proper Communication.