Yes, you can purchase only hosting services with us. To use our hosting service, you do not need to register or transfer your domain to us. If you keep your domain registration with another provider, you need to change your domain's nameservers to point it to our server.
You will get the nameserver information (NS information) from our login details email.
If you do not want to change the nameservers and just want to update A and MX records, you can submit a ticket from your client area to obtain the necessary DNS records.