As stated there is no charge for dialing 1471 , but if you chose to ‘return the call using BT’ by dialing 3 then there is a 35p charge for the facility, so it’s either someone did dial 3 after 1471 , or it was some sort of one off glitch , obviously you and BT may have different views on what happened.
As you said it’s the principle not the 35p , so rest assured 1471 is still free , returning the call via this method isn’t , if you are adamant the charge is wrong and neither yourself and no one else with access to the phone used 1471 ( which you obviously are familiar with and use ) but didn’t use the return call option , it’s pretty certain that BT would waive the 35p if you dispute it.
