Why this huge difference in line capacity detail?

[#1]

After an engineer visit a few weeks ago my line suddenly shot up to a potential of 4000+ Kbps. It had always shown a maximum capability of 0-2Mbps. After weeks of having a connection speed which gave me a 3Mbps profile I have been having strange DLM interference resulting in large speed drops and lowering of IP Profile. Having been in contact with PN via phone several times I keep getting a difference of opinion as to what the problem is. Yesterday I was told that my line is definitely a 0-2Mbps line and that anything above that is because my line is
"overperforming" ! Overperforming by by DOUBLE??? Last night I noticed my connection speed had suddenly dropped to 1664kbps from being 3328kbps in the morning. I will add snapshot pics to prove, taken from DSLstats data. When I asked PN about this I was told that because my line is 0-2Mbps it was not a fault and anything above that was a bonus due to overperformance of the line!
I was irritated by this response and rebooted the router and was reconnected at 3264kbps. I have been doing BTwholsale Speed tests over the last few weeks and can prove that my line is 7.15Mbps capable NOT 2Mbps but no-one at PN believes me. This morning I did a BT test and the result shows my line as 0-2Mbps capable and an IP profile of 1.25, yet I am connected at 3264.
How can this be?
Attachment 1 This mornings BT test
Attachment 2 Previous BTtest
Attachment 3 This mornings telnet data.

[#2]

I'd guess that BT Wholesale has upgraded some kit at your exchange, but not yet got around to updating the exchange data?
Once the BH is over the Operations guys can check with BT.
M

[#3]

I have never thought the "max achievable speed" reported by the bt speedtester is of any great importance.
The speedtester reported 0.4-2 because your IP profile was 1.25 at the time of the test, it reported 0.6-7.15 because your IP profile was 2.5 at the time of the test. Probably the speedtester should report the max achievable speed as equal to your IP profile to avoid the confusion. It should indicate the maximum possible result of the speedtest, not imply some sort of maximum capability of your line.
If your line DSL sync speed improves, the IP profile increases, and the range reported by the speedtester may then increase. But it certainly doesn't mean your line is capable of reaching 7.15Mb.
Those IP profiles to the nearest 0.25 or 0.5 indicate the exchange is still 20CN so I doubt anything at the exchange has been upgraded.

[#4]

Can you provide full line stats from your router please?