26/02/2024 = Date of issue and presumed date of posting of the NoR.
28/02/2024 = Deemed date of service and day 1 of the 14 & 28 day relevant periods.
12/03/2024 = Day 14 of 14 = last day to pay at discount.
26/03/2024 = Day 28 of 28 period.
So you've left the discount option lapse, although you might find that the computer system doesn't update until this evening.
Does that mean you intend to appeal to the Adjudicator? In which case it's all or nothing. Nothing if you win and £130 if you lose.