Absa credit card division

To ABSA credit card division Today I received a sms from you informing me that interest on my credit card wil now be charged on the 15th of every month. I find this very suspicious. I pay my card after the 15th of every month. Usually on or after the 16th. This is before payment is due. My feeling is that you realized that if you charge interest sooner you will be able to charge more interest. Now interest will be charged just before I pay. It may be legal, but if this is the case...it is not very ethical on your part. I've tried contacting you about this (a phone number was provided with the sms) but I gave up. I had to hold on forever. But now I will just pay my card on the 14th of every month. As I say not very ethical on your part. If this is not the case I apologise. But I have a feeling I am correct. Why the change in date? Explain it to me. Was the date changed to the 15th of every month across the board or was it done individually? The interest I have to pay extra will not be a lot, for I do not owe much, but it is the principle that counts.