There is no need to explain. It is very simple. Either they did let you go on it, or you aren't on it.
It may have taken some persuasion on your part, but that doesn't mean they didn't allow it.
They didn't allow it prior to October unit price cap......once October kicked in, i was then covered by the new unit price cap, but wasnt from the time i switched up to October 1st.
Therefore for a few days in September i was subjected to their offer to switch rate of 55p/kwh electric and 24p/kwh for gas, because it was my choice to switch.....as i was then a customer, when the October 1st unit cap came in, they had no choice but to allow me to be switched to the standard rate covered by the government
Previous to October 1st there was a unit price cap, of around 27p/kwh for electric and 7p/kwh for gas......which in monetary terms for the AVERAGE household was around £1980 per year.
I hope this clears up the matter, but im guessing it wont, as you know more than anyone else and like to tell people that you do.....but in the rule world its not.