Once you have the Merchant number then everything is Down Hill sailing.
 Because you now can ring and do your own Credit Checks straight with
the Company who owns the Card you are using.
 What you do is :
                 1.) Ring up Bankcard, Mastercard, Visia, American
                     Express ETC, and quote the Number of the Credit Card.
                 2.) They will then ask you for your Merchant number
                     to them the Merchant number is just the number of the 
                     Shop listed to them.
                 3.) Quote them your Merchant number.
                 4.) They will then Check the Merchant number
                 5.) If all is well they will proceed with the Credit
                     Check.
                 6.) They will come back and requote you the number
                     of the Credit Card.
                 7.) Then they will tell you how much Credit the Card
                     has on it and how much can be used.
                 8.) Say thanx alot then hang up.