Sorry to hear you're no closer to getting it resolved.
From our side, the second form they sent out has finally arrived 6 days after the date they printed/sent it - the first form, allegedly sent on 25th Jan, never did arrive. The form we received says we need to complete and return it within 14 days of the date of the letter, which is amazing when they've already used up 6 of the 14 days to get it to us in the first place!
We'll get it signed and returned by special delivery so there's no excuses for having not received it and see what happens after that.
I am experiencing the same problem with my 84yr old mother. I have been trying to get her on to the BT basics package. She has now sent 4 forms and qualifies, I have been told several conflicting reasons none of them true. I am now going to reopen a complaint I made after the third form was not accepted with no explanation. I have spent over 2hours on the phone speaking to several different people none of whom seem able to resolve the issue. I am begining to think its all a con. I have been sending forms since early Feb and they are still charging my mum the full rental