Annual Fee and Monthly Fee

With the new system of billing card fees monthly one would expect this to begin only after the previous annual fee (paid in advance) was utilised. However I was charged a monthly fee on my most recent statement whilst having paid an annual fee less than 12 months ago. Call centre notes that \refunds"for proportionate annual fee will be posted in future as they are delayed but they are starting to bill monthly from February. How though can you double charge first and then refund when you feel like it the following month? I settle my entire account monthly to avoid interest. So if I were to decide not to pay this invalid fee I would be charged interest. Also"