rate come down, but my bond repayment goes up?

Very disappointed and disgusted. Just received letter from Nedbank in terms of our home loan. The rate has reduced by 0.25%, however the repayment now instead of reducing, increased by R154? I fail to understand how this was calculated especially if one applies simple math. If a rate comes down, then surely your monthly repayment must also come down. Tried to call the call center taking the number on the letter. 1st I was kept on hold and then instead of being out through to the home loan section, I was in the queue for the collections department?? The bond will be registered now 19 Oct being 13 years, however the term outstanding on the statement also appears to be incorrect and reflects as 86 months? We have never been in arrears and bond is close to half of the registered balance. I need urgent clarification how my bond repayment could go up if rates came down