linux - Create a crontab script with curl

Trying to set a cronjob to use with curl. Want to update IP on noip.com. The command below gets the IP from noip.com but does not update it with my servers ip. I mean: when the IP is not updated then I get the old one:

curl -X GET 'https://dynupdate.no-ip.com/nic/update' --header "Authorization: Basic $(base64 <<< $xxxxxxx:$xxxxxx)" -d "hostname=$xxxxx.ddns.net"

this command below poduces error sh: GET: command not found

ExecStart=/usr/bin/curl-X GET 'https://dynupdate.no-ip.com/nic/update' --header "Authorization: Basic <$xxxxx:$xxxxx>" -d 'hostname=.xxxxxx.ddns.net'

Need help for an appropriate script