You cant change the ONT on your own, the serial number on your existing one is linked to you and it matters im afraid.
Just wanted to say thanks to everyone on here for some of the great suggestions in trying to get this matter resolved.
In the end, BT sent out an Openreach Engineer who swapped out the ONT from a 1GB LAN version (Yellow RJ45 port) to a 2.5GB version (Orange Rj45 port). I believe they also did a reset on the line. Perhaps a combination of both resolved the problem in the end. 😕
Just a bit disappointing that I have had to battle so much with BT CS for them to acknowledge the issue, instead of throwing Ts and Cs at me.
That’s a good outcome, unfortunately with the way Ofcom requires Openreach to communicate with ISPs not allowing you to speak directly with the network provider , and generally ISP customer service representatives are not necessarily ‘technically minded’ you can come across the ‘it’s working within the acceptable limits’ script , but with perseverance you got there in the end .
No way to know if it were the ONT swap , or the registration of the new ONT cleared up some dodgy data , that fixed the issue , but it doesn’t really matter if it’s fixed .