Had repeated problems with the 2 Factor Authorisation (where you have to enter '#' on your phone) to confirm a transaction where no matter how many times you try the hash key is simply not recognised.
When I complained they said is due to my mobile provider and their poor quality compression of reverse DTMF files. I tried to explain that on multiple occasions the problem simultaneously occurs on both my mobile and landline (and the same on my wife's account) which are with different providers. I also made an attempt to explain the chances of that happening simultaneously (multiple times/multiple accounts/multiple provider) and suggested that actually it could only be due to a single source (i.e. their system) but that didn't compute. I thought momentarily that I would try to create an analogy with ETOPS but then decided that life was too short.
However what is worth knowing is that if you phone them direct you can sell (you can buy without logging on with just a Direct Debit) as long as you can answer the various security answers.