I did a bit of searching to try and get some line stats so we know what the router is thinking when I came across
this thread on the TalkTalk community. Seems the router was faulty but it took someone with a very technical mindset who was actually able to compare with multiple routers before support would do what needed to be done and replace the router.
I can't find, in the online manual, which page has the line quality stats on it. You need that if you are going to argue with them.
There is, however, one thing you can do yourself just to see.
Open a command prompt by holding down the windows key and pressing the R key. In the run dialog type cmd and click on OK.
In the command prompt, copy and paste this line.
ping -t
http://www.google.co.uk >%homepath%\desktop\pinglog.txt
press enter and the cursor will just sit there blinking. Leave it for one hour.
After one hour just close the window by clicking on the X in the top right of the window.
On your desktop you will find a file called pinglog.txt. or just pinglog with a notepad icon on it. Double click on it and you will see something like the text below.
As you can see I'm getting about 40ms response time. time=40ms. For you it will be faster because I'm in France. However what you are looking for is odd time values like time=120ms or higher and, even worse, a line which reads that the ping timed out waiting for the result.
If you get anything like that in the list, at all, then you have a problem with the line.
It's best to do this on a cable connection, not wifi, but either should do it is just that the wifi will give less regular results. My variance is no more than 4ms, however on Wifi it could easily be 10 or 20 especially if someone walks in front of the signal. however it should never be 80 or 90 and it should _never_ time out.
Pinging
http://www.google.co.uk [216.58.198.163] with 32 bytes of data:
Reply from 216.58.198.163: bytes=32 time=40ms TTL=53
Reply from 216.58.198.163: bytes=32 time=40ms TTL=53
Reply from 216.58.198.163: bytes=32 time=40ms TTL=53
Reply from 216.58.198.163: bytes=32 time=43ms TTL=53
Reply from 216.58.198.163: bytes=32 time=39ms TTL=53
Reply from 216.58.198.163: bytes=32 time=39ms TTL=53
Reply from 216.58.198.163: bytes=32 time=40ms TTL=53
Reply from 216.58.198.163: bytes=32 time=40ms TTL=53
Reply from 216.58.198.163: bytes=32 time=39ms TTL=53
Reply from 216.58.198.163: bytes=32 time=40ms TTL=53
Reply from 216.58.198.163: bytes=32 time=40ms TTL=53
Reply from 216.58.198.163: bytes=32 time=40ms TTL=53
Reply from 216.58.198.163: bytes=32 time=39ms TTL=53
Reply from 216.58.198.163: bytes=32 time=40ms TTL=53
Reply from 216.58.198.163: bytes=32 time=40ms TTL=53
Reply from 216.58.198.163: bytes=32 time=41ms TTL=53
Reply from 216.58.198.163: bytes=32 time=40ms TTL=53
Reply from 216.58.198.163: bytes=32 time=40ms TTL=53
Reply from 216.58.198.163: bytes=32 time=40ms TTL=53
Reply from 216.58.198.163: bytes=32 time=41ms TTL=53
Reply from 216.58.198.163: bytes=32 time=39ms TTL=53
Reply from 216.58.198.163: bytes=32 time=39ms TTL=53
Reply from 216.58.198.163: bytes=32 time=40ms TTL=53
Reply from 216.58.198.163: bytes=32 time=39ms TTL=53
Reply from 216.58.198.163: bytes=32 time=41ms TTL=53
Reply from 216.58.198.163: bytes=32 time=39ms TTL=53
Reply from 216.58.198.163: bytes=32 time=40ms TTL=53
Reply from 216.58.198.163: bytes=32 time=40ms TTL=53
Reply from 216.58.198.163: bytes=32 time=40ms TTL=53
Reply from 216.58.198.163: bytes=32 time=40ms TTL=53
Reply from 216.58.198.163: bytes=32 time=40ms TTL=53
Reply from 216.58.198.163: bytes=32 time=40ms TTL=53
Reply from 216.58.198.163: bytes=32 time=40ms TTL=53
Reply from 216.58.198.163: bytes=32 time=40ms TTL=53
Reply from 216.58.198.163: bytes=32 time=41ms TTL=53