Engineers are ment to where feasible to change an master socket for an nte5 whilst at a property (some times time or access restrictions mean it may not get done on a visit assuming the master socket wasn't part of an issue to do with the visit).
As to requesting a visit specificaly to change a master socket to an nte5. I'm not sure, there are so many changes lately with what specificaly is & isn't chargeable and some thing called WLR3.
As stated on this string, confirm this with your telephony service provider (SP) not your iternet service provider (ISP) first