Sigh - yet another battle with BA for my already ticketed DONE4

I am looking to change the date on one of my flights which I confirmed when ticketed that all changes of dates were free - in looking at the fare rules it just says that changes are permitted but it doesn't say for free and it also doesn't say there is a charge for changes (unless you are changing the routing etc).

Has anything changed with the rules or can someone confirm:

a) All changes to dates are free (where does it actually say they are free or no charge)
b) There is no re-price or re-quote on date changes

The fare rules on the oneworld site seem to indicate the above - from the rules it says: Rebooking is permitted as long as the routing remains the same

I assume a change in date does not mean the ticket needs to be re-issued which would be a $125 USD fee