Had a similar problem with a "H" fare in CDG in July. The BA agent refused to put me on standby for an earlier flight ( I was 3h early), telling me my ticket was a restricted ticket - for the price, I like to call it "semi-flexible".

In the end after some stern looks, hands on hips and polite instance by me that it was changable, I was allowed on the flight, paid the change-fee (with credit card, apparently someone had recently used forged bank notes to pay a change fee the week before ).

As punishment she did book me into a non-tier point earning class which I subsequently had to get the EC to correct.

Perhaps "H" means different things in different places?