Unfortunately once registered and paid can not change only after one year just don't renew it.

No once you have decided on your name and you register it it's a done deal.

If you have registred a Domainname, you can't just change it. You have to register a new one, and pay for that too. The "old" domainname remains for one year. You have to renew the abonnement for domainnames once a year. If you don't want the old one, you have to deactivate it.

Nattawut (Amgolf) below has given you the tip to redirect tho old site to the new one. If you want to do that, I suppose you should not deactivate the "old" domainname. If you look at the training Nattawut suggested, then you'll get the answer how to do that.

:-)

You should redirect the old site to the new address
because some old post drawing traffic will remain. Two Ways To Create A 301 Redirect