Definitely agree with the OP on this topic when it comes to amendments to bookings with BA. They aren’t deliberately out to overcharge, but I have had a few instances where the system has produced an inflated number and luckily I have caught it. In one instance the GGL agent actually worked it out manually to check after I queried a tax change and his and my figure aligned at over £150 less than what the ‘system’ had calculated, so if you are changing any details in an existing booking - have an idea of what you expect the tax difference to be prior to the call.
Pilot37