Hi Brett, sorry to hear you're having phone issues and welcome to the Community Forums.
I've tested your line from this side and it isn't finding any faults whilst testing although it doesn't necessarily mean there isn't one. It does mean however we would go down the route of arranging an engineer to come out and investigate however before doing so I'd recommend doing 1 check your side to rule the problem out from being caused by something internal.
If you could plug the phone directly into the test socket behind the faceplate of your master socket, this will rule out internal wiring, extension sockets and the face plate it's self which can all go faulty.
For the sake of ruling as many things out as possible I'd also recommend disconnecting the router for a period of time in this set-up so you can try the mobile call again to see if the same thing happens. If possible I'd also recommend trying another handset as this could be the cause.
How to locate the test socket and set your connection into it can be found here:
https://community.plus.net/t5/Library/Testing-From-The-Master-Socket/ba-p/1322242
If the problem persists from here we know it's nothing internal and we could safely go down the route of an engineer without the risk of £65 unneeded engineer charge if the problem was found to be with one of the above things. (Although the charge could still be applicable if the arrange appointment was missed or cancelled within 2 days of the appointment.)
Let us know how it goes after the above check.
Kind regards,
