@dja76 Plusnet staff support, like the phone service, is still severely restricted. If you would like help from the community, a good starting point is to have a look at This post and supply as much detail from it as possible.
It would also be a good idea to carry out a 'Quiet Line Test' - dial 17070 from a (preferably corded) phone and select option 2 - there should be no discernable noise. If there is, report a phone fault first, as without a clear phone connection, your broadband will not perform correctly.
It may be an idea to also report your lines capabilities - please post your results from THIS site, but ensure your phone number is obscurred/hidden.
If you reply to this topic with as much detail as possible, there are plenty of experienced members who can advise on possible remedies.