Making sure I receive commission

Hi!
I'm affiliated with hosting companies, and for some reason I don't get commission for every sale I drive (I contacted my customer and saw that they signed up)
1. Is it possible that they have a cookie of a different affiliate on their browser?
2. Does the new Cookie overwrite the old one?
3. How do I make sure to receive commission for each sale?

Thanks.

Usually the payment is done on a monthly basis (or two weeks), you can check your stats on the dashboard I guess. And affiliate network will need you to use specific link which can give postback info.
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i this there is no chance to track if you get every commission ....... you can track what you sent there and if the return is to low change the network.