Hi Unicorn,
Now you're logged in on Router...........From the menu look for Network and the DNS input Boxes will either have the Movistar DNS numbers or be Blank,
Change to the SmartyDNS ones.
Now I better look for the manual .............
The manual even..............

Section 3. is the bit you need.
https://en.admininfo.info/manual-para-c ... a-movistar
UNIX is basically a simple operating system, but you have to be a genius to understand the simplicity.