Can I change my domain name?

No, sorry. That's the nature of domain registration. Once you have registered (purchased) a domain name it's yours to keep. So be careful to double-check for typos!

What you can do of course is just register the new domain as well, and then let the old one expire after the period you've paid for passes.

Keep in mind that you may opt to re-direct the old domain to the new domain. And you can park the new domain over the old one.

On the hosting account, if you want to switch your domain with a new one, you can do that by opening a support ticket.