British Airways flight cooling off period

I recently booked a flight with British Airways, and made an error with my booking. I understood that if you change the flight within 24 hours there should be no penalty. I changed the flight within 1 hour and was charged £35 service fee for making the change. Having phoned British Airways I have been told that because I made the change online, and did not speak to a representative this fee will not be refunded. Every other change that it made with British Airways they charge if you speak to a representative. I have been told that I will get no refund and that I should take a note that if I need to change a flight within the cooling off period in future I have to do it by phone.
Many travellers will notice that British Airways is beginning to behave more and more like some of the poorer budget airlines. I am a very frequent traveller and would like other travellers to be warned.