Do not stick to agreement

I went to olyn during November to make arrangements on an account to do the payments which I sticked to the agreements and made the payments as promised and agreed but everytime I want to buy electricity my card is blocked!!!! I made a payment before the date that we had agreed on but last week I had to ask them again to open the card and today I wanted to buy electricity again just to hear that the card is blocked again even though I did stick to the arrangements! I would appreciate it if they can give me a GOOD explanation for why they do this???? I can understand if they blocked the card if I did not stick to the arrangements but why block if I did everything I am supposed to do!!!