fibre or not??

[#1]

hi all,
new plusnet customer since March 12th, on unlimited fibre.Had an email from plusnet support telling me that my line is slower than they quoted it would be. Plusnet quoted between 11-18mb. i am currently getting 4.6 wireless and connected by cable, this is only 1mb quicker than the adsl connection  i had on TalkTalk. Could there be a situation where i am connected by adsl and not fibre? is there anyway of finding out? everything on my account says i'm connected by fibre.
have ran the BT Wholesale speed test which says 4.6 and the line is only capable of 5.2 which is exactly what plusnet are telling me.
anyone have any ideas?

[#2]

Your definitely on Fibre
The estimated line length for your line is 1.8km so it may be your too far from the cabinet to get the estimated speeds.
We'd recommend raising a fault so our Faults team can have a look.
https://faults.plus.net

[#3]

Hello Matthew,
thanks for your reply, will raise a fault as you suggest.
thanks for the link.