Rejected BT Basic, advice pls!

Supa

I've been on income related ESA long term due to having a lifelong disability and first applied on 3/9/20. I was told I had to be on a BT contract so asked what their cheapest tariff is, they said it would be easier to transfer if they put me on their standard tariff, £27 a month plus £20 activation fee but they said not to worry as I would be refunded the difference and activation or could cancel if I got rejected in 2 weeks, and that as long as I'm receiving the eligible benefit I'm entitled. So after a month I received a rejection letter (10 days from the date on the letter) they sent out another, another month later and I got rejected again. Both times they gave no reason for why I was rejected, and they've said they can't give a reason and I can't talk to a manager, I just have to wait for another form so I can send it in again.

I've asked DWP to send me another proof of ESA letter so I can scan it and email if necessary as proof that I've been in receipt the whole time. The problem is I've payed much more than the next cheapest tariff available at the time and was thinking about maybe trying to contact CAB? I don't understand why they have created such a convoluted system just to apply, it's fine if it goes through like it should (as I'm sure it does for many people) but it seems if anything at all goes wrong, they refuse to help in any way. I've asked to make an offical complaint but the guy said his team manager won't be able to say anything different and has no power to do anything. I insisted I wanted to speak anyhow. This whole situation has been a source of anxiety for me, surely the government funded this tariff to help people, not cause more stress just to apply? Shouldn't BT be accountable for setting up a system which is unfit for purpose in the case of incorrect rejection? 

macman

Make a formal written complaint. If no response or resolution after 8 weeks, go to the Ombudsman. 
Pointless advice just to keep reapplying if you have already shown evidence of being in receipt of ESA
CAB are not going to be able to do anything you can't do yourself.