For enable telnet: download the discus from the router and open it with a text editor (Wordpad, Textedit...) and find this:
(telnets
(disabled(1))
(ports
You change it with:
(telnets
(disabled(0))
(ports
Upload the new file in the router and wait the reboot
Now the telnet is enabled on the router: WIN+R --> telnet 192.168.1.1
Let's disable TR069C, for do this go to Remote Administration, and do not the flag on TR-069
Now from telnet write this:
conf set /cwmp/enabled 0
conf reconf 1
Your ISP is PPPOE or PPOA?