What could Openreach have done to my line?

Question

I had a line fault. The Openreach engineer said there was a loose wire in the box down the road and it's now fixed. 
Trouble is, afterwards my broadband speed (Sky) had dropped from over 5mbps (for the last 8years with different providers) to 3.5mbps.
BT said speak to your ISP. But Sky said the line won't go any faster. I switched ISP in a huff, and it looks like it's the same with the new ISP; they (Zen) said the same, but to let it train. But it's 3.5mbps and doesn't look like it's going to change. 
I'm in the test socket, quiet line test was quiet. Also, new router and filters.
It looks like BT will just say, there's no fault i.e. "we're a monopoly and we can be as rubbish as we like." 
What could the Openreach "person" have done in that box?
FWIW, here's some stats:
Uptime:
1 day, 5:27:46
DSL Type:
ITU-T G.992.3
Bandwidth (Up/Down) [kbps/kbps]:
1.095 / 4.099
Data Transferred (Sent/Received) [MB/GB]:
110,54 / 2,19
Output Power (Up/Down) [dBm]:
12,8 / 0,0
Line Attenuation (Up/Down) [dB]:
26,8 / 43,0
SN Margin (Up/Down) [dB]:
5,8 / 6,1
System Vendor ID (Local/Remote):
TMMB / ----
Chipset Vendor ID (Local/Remote):
BDCM / IFTN
Loss of Framing (Local/Remote):
0 / 0
Loss of Signal (Local/Remote):
0 / 0
Loss of Power (Local/Remote):
0 / 0
Loss of Link (Remote):
Error Seconds (Local/Remote):
125 / 0
FEC Errors (Up/Down):
0 / 0
CRC Errors (Up/Down):
742 / 181
HEC Errors (Up/Down):
567 / 596

Answer 1

Fredstone wrote:
I'm already in contact with Zen. But they will be at the mercy of Openreach too.
Openreach is not a separate company. They're a division of the BT group (although they're supposed to operate independently).  They are totally independant under OFCOM rules
When the line fault occured (phone dead), BT - who own the line and are the phone provider - were the correct port of call and responsible for testing the line and sending Openreach to fix it. Openreach didn't fix it (manifestly). But on talking to BT again, they're able to claim it is fixed when it obviously isn't as far as broadband is concerned. So nothing further gets done - unless Zen can persuade Openreach to do something in a week or so's time.
I was hoping for any insight as to how BT's lines could have become "degreaded" in this way at the hands of Openreach. As well as highlighting the absurdity of it all.   There is no such thing as a  BT line the network ond owned and operated by Openreach for all service providers        
Yor phone and broadband problems are seperate issues Openreach have repaired your voice line fault it is now down to your ISP to deal with Openreach to resolve your Broadband problem 
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