This is something that your ISP should arrange with Openreach.
Openreach have come up with stringent "address matching" rules that an ISP ought to have followed when they booked the service in the first place; these rules end up being based on either matching an address that they already supply, or falling back to the PAF (post office address file).
But all of these rules are things to be followed by their CP customers, not by you.
Some of the initial guidelines can be found in section 3 here:
That document defines some of the interaction that should go on between an ISP (aka "CP") and Openreach; note the mention of Gold, Silver, Bronze and Temporary addresses.
There is a more complete description of address matching hidden within Openreach's "Best Practice Guides" for their CPs. I found a copy here:
Your issue might be related to slide 10. Solution might come in slide 16 or 20, but slide 27 is probably most relevant.
In some of those slides, you'll see mention of an "Openreach Data Integrity" section, and robot. It might well be the ORDI team that needs to deal with your issue.
If Plusnet aren't playing ball, perhaps you will need to mention that you want to get the "Emergency Services Database" correct. It is one thing having Openreach engineers going missing, but quite another when that 999 ambulance gets lost.