When I try to purchase it says there are too many Chargebacks

When you chargeback on any server you increase your "risk threshold". This means that, depending on a server's risk threshold you may not be able to purchase from a server.

To be able to make a purchase you must settle your chargebacks on the server(s) you have charged back on.

If you have charged back on Cosmic, you'll have to email [email protected].