D-Link DSL 2750U is a ADSL broadband wifi router.
It has rj11 port for wan connection.

For ethernet cable internet like - Tikona, PMPL etc they are giving rj45 cable port for wan setup.

In this video guide for convert one LAN RJ45 port as a WAN port

the russian firmware link--
ftp://ftp.dlink.ru/pub/ADSL/DSL-2750U/Firmware/