Blueface changing policy and applying it retrospectively

I was fortunate enough to spot that Blueface had charged me peak rates for the past couple of Bank Holidays. I brought it to their attention and they sorted the problem out. This happened on another occasion too.

I brought this to the attention of other Blueface-ers on boards.ie.

Blueface's solution to the problem would appear to be to change the policy so that public holidays are no longer considered off-peak. They only introduced this policy in the last couple of days and are applying it to at least the most recent 2 bank holidays.

Can they apply this policy retrospectively like this?

Well if would appear to be a non-issue now. They have clarified that the new policy will be applied from today. But if there are any subscribers on AAM, it might be worth checking calls made on previous bank/public holidays so that they can correct your balance.