On the new ones that fit an NTE5C the switch is on the (I think) left hand side.
Ah, I don't have that faceplate, the Master Socket 5C that I have on my desk only has the combined phone and dsl faceplate.
The Engineer that did the internal work for my FTTP install said that he could install the new 5C Socket, but the current 5A is more solid compared to the 5C, and said it might be better to keep that considering it was brand new.
Sadly he didn't have a switchable phone line faceplate for the 5A in his van.
This was why he removed the dsl filer faceplate and left the cable in place ready for FVA to go live over the next few days, where I just had to remove the old copper line and connect the new cable, which is easy to do.
The only hard part for me to do was getting up off the floor LOL