The RJ-48 connector look very similar to a RJ-45 connector drawn. But its different. RJ-48 connections are made with a STP (Shielded Twisted Pair) cable (not UTP - Unshielded Twisted Pair). RJ-48 uses a pin out arrangement, voltage level, and line capacitance different from a typical RJ-45.
Cable for conection of WAN port with wall outlet is shielded (STP) straightforward (R to R, T to T) with R with T, R1 with T1 wires twisted.