Mismatch between my BT IP profile and my Plusnet IP profile

[#1]

For the last 2 years my download speed has been on average 4000 kbps (sometimes as high as 6200 kbps) but 2 weeks ago it dropped to 131 kbps and has stayed there, until 5 days ago when it went up to just 237 kbps and has remained constant since then.
I have tested my router (Netgear DG834G) on another line (it works fine) and have tried a different router on my line but it still downloads at 131 kbps.  I have eliminated other internal interference, by testing on the master socket and by using a different PC. So I don't think the fault is at my end.
I have run BT speedtester with the following results:
Test1 comprises of Best Effort Test: -provides background information.
    Your DSL connection rate: 6752 kbps(DOWN-STREAM),  448 kbps(UP-STREAM)
    IP profile for your line is - 5500 kbps
    Actual IP throughput achieved during the test was - 99 kbps
My IP Profile on PlusNet site is showing a Current line speed of 250 kbps
My router is showing
ADSL Link                 Downstream          Upstream
Connection Speed 6752 kbps                448 kbps
Line Attenuation         17 db                         5.5 db
Noise Margin        10 db                          24 db
It seems there is mis-match between my BT IP profile and my PlusNet IP profile. Is this what could be causing the problem?
Can anyone suggest what I need to do to get them brought into line please?
I raised a ticket for the problem on 27th Nov (ID: 27134957)  but so far I have got nowhere, and now  I can't seem to get a response from Customer support. I think they have given up on me! 
Many thanks

[#2]

Give me 5 minutes, then reboot your modem/router and see if the speed improves.
There have been far too many of this type of query over the last few days, something is definitely wrong somewhere.

[#3]

Hurrah! 
I am now getting a download speed of 5202 kbps
2 weeks with no result, resolved in 5 minutes by you!
Thanks Chris, you are an absolute star!
I can get on with my Xmas shopping now
Thanks again

[#4]

No problem, glad I could help.
Now to go raise a problem as this is happening too frequently, the profile we can see in the BT  reporting system we use still shows the lower profile so in theory that should be your IP profile.