@vikorr,
Very good advice, vikorr! One thing I HATE is for someone to give a false, self-serving apology. Ask yourself what your part in the wrongdoing really was...and then, recall exactly what you apologized for and if your apology was sincere.
I have theis completely retarded, yet INFURIATING story... An older woman in the family took a picture of me in my underwear at the beach, and I was completely unaware she was doing it,...until I saw it online in her photo gallery, where several other people I knew could see it.
I had TOLD HER EXPLICITLY the day before and at least two other times that I have a weird thing about being photographed and for her please not to take any pics of me.
She acted all innocent and apologized because "I was upset that she didn't delete the picture before she downloaded them all online". The apology was just as bad as the infraction.
Think about what you actually did, and if your apology addressed it.
If the apology sucked, think about what you really did and offer a sincere apology of ownership for it. It may be that you do this same thing a lot and they are tired of dealing with it.
OR, they may be mean asses.
Anyway, only one sincere apology is necessary. More would be useless and demeaning to you.
Do you want to share the history so perhaps we can help?