Sound advise there RobertoS,
I think he was advising that PN may have ordered the 40/10 product for you, rather than having the wrong value stored in their database.
But if that were true, your sync speed wouldn't be in the 70's and the IP Profile in a BT speedtest wouldn't be in the 70's. They'd both be around 40 or just below.
But it was indeed sound advice to get in touch with the support guys by phone.
They must be saving a mint by automatically under-setting their customers profiles.
The profile value kept by Plusnet isn't a value set by them once and kept forever.
It is meant to be dynamically updated based on the actual speed of your line, reported by BT, using BT's automatic updates. That value is normally updated when your router connects through your modem or (like you are currently doing) your PC connects direct to the modem.
Plusnet have to put some initial value there, so that things keep working even if BT never send an update. Normally, they'd put a value of, I think, 77.4Mbps there.
If it has gone wrong, it is because PN put the wrong initial value in there, which will get updated later, or BT has sent the wrong value.
The bottom line is that it should change automatically for you.
So - if you aren't yet sorted out, you could try disconnecting your PC, waiting a minute, then reconnecting.
If that doesn't do it, you can disconnect the PC and power down the modem. Wait a minute, power up the modem, wait a minute, connect the PC (Only power down the modem once, so we don't trip DLM).
Or, of course, wait for PN's support team.