I think you will have to get back on to Sky. Your line is probably fine, the problem is with the exchange setting. Try this first-
Go to
BT Speedtest enter your phone number then your ADSL username. This will do an official BT speed test and show your present profile. Your ADSL username is <the MAC number of your router, no colons, followed by> @skydsl You can also obtain this from the router by using one of the utilities available on the forum. This tester is always busy, it could take several attempts to get on.
You should be able to use this report when phone Sky, but it will depend on who takes your call as Sky T1 do not seem to be trained for Connect customers. If you can get them to pass you to the CST, they will be able to assist you. If they refuse to put you through to the CST, use the
KANA Form it may take a bit longer but it will eventually get to those who know what to do. Copy and paste the result of the Test into the form and they will get an idea what is wrong.
Your line profile may have been set too low and may have to be adjusted by BT. It could take a few days, as Sky have no control once they pass it to BT.