You don't need to store the credit card information if you are using paysystems. They will take care of it. Do note that storing information such as credit card numbers can cause enormous implications if you ever get it stolen.
On the other hand it does help you if you ever stop using Paysystems. You do have to details to make a transfer easily.
To echo what Sprintserve said, it carries enormous liability to store credit card information. In fact, if you are not in compliance with the criteria the credit card companies set down to store this data you can lose your ability to accept those credit cards.
Yes, I would recommend against storing cc numbers. Let the experts handle this (the payment processors). If you want to store the cc number for verification purposes (ie. asking the customer to re-confirm details etc), store a hash of the cc number instead (ie MD5).