As suggested by nearly every comment.
The salesman does not sound very honest or helpful.
If it was me, I would go to another garage. If you cant get the salesperson on the phone, you could visit and cancel your order.
I phoned Motability to cancel an order and the helpdesk said I must phone the dealer and cancel there. They could not do it, must be the dealer.
But if you want to keep with that dealer, get them to amend your order to the lower AP as suggested.