mWEB of deceit and misleading fibre packages

not sure whether I listed the correct mweb but I will write my report regardless.

years ago I had an account with mweb and had a adsl connection with constant issues.I cancelled back then after poor service and was hoping that they have grown since then.How mistaken I was. I changed my fibre provider to mweb and never ran speed tests because supersonic always provided on average 18mbps via mitchells fibre. I now have a 28 day voucher for uncapped fibre where the package is supposed to deliver 20mbps. I however am getting a lousy 3...THREE mbps. I see this as theft to say the least. I have ALREADY paid for a service which I am NOT enjoying. when I called earlier I was number 30 in the line for technical service,which CLEARLY speaks volumes about what they delivering. I have no debit orders,it is a month to month voucher,so I need to know HOW this provider will compensate me for a service they charged me for but can't deliver