Residential DSL is a best effort service that doesn't have a speed guarantee as it can be affected by factors like the distance you are from the local exchange, copper quality, number of users sharing the line.. etc.
However, if you log into your modem and copy the DSL info and paste it here, we can get a better idea of the line stats of your DSL connection. And have you spoken to anyone from tech support yet? There is a chance that you could have been provisioned on ADSL by mistake.
It really depends where you live. I changed mine from ADSL to VDSL last week and I only got speed bump for about 1.8 times. If you're house is close to Vodafone landline box, you'll get the best speed that VDSL service can offer.
My address also shows I'm connected to ADSL still but im on VDSL. You can check your connection whether you're on ADSL or VDSL in your Vodafone Home Gateway in "Internet" section. It'll say Internet_adsl or Internet_vdsl is currently "connected".
Not the only one mate, I live close by a cabinet i.e. it's on my boundary have paid for VDSL but getting ADSL ... how I know you ask? I set my router to connect by VDSL and no luck connecting, set to ADSL connects.
See if you can configure your router to connect specifically via VDSL as I did, then complain because Chorus probably configured the service incorrectly on installation (of course you can't complain directly to Chorus you have to complain via the appalling Vodafone call centre in the Philippines).
Vodafone service isn' what it used to be, I am currently trying to get them to fix it.
Yes, They asked me to be home and keep looking to my modem while the factory reset it. Not really sure why do they need me to looking to flashing lights at my modem. What also frustrated me is that when I was talking to the support the lady said I was getting 30+mb and the problem could be my wireless connection. That doesn't make any sense because I was testing using a wired connection straight to the Huawei modem provided by them. And also that is exactly the same gear I used to get 40+mb in my previous address.