Discharge figure

Hi All, I've been reading for a long time but rarely post. In fact, I can't remember my old account.

Anyhow, I am selling a property on behalf of my parents.  They currently have the mortgage with HSBC.

Back Story **************

All the necessary paperwork was sent via my solicitor to the bank close to around mid-July.  I also needed the title deed to be re-produced to a single name due to a death.  The notice of death again was also sent to the bank in mid-July.

The original settlement date was 9th August.  On the 7th, I decided to call up the relationship manager to just get a confirmation on everything.  To my surprise, I was told that the title deed was not reproduced as the paperwork was still sitting in their 'backoffice' and the loan could not be discharged.  My solicitor and I then rang pretty much 2-3x a day for the next 1.5 weeks and I even went to the branch myself.  The answer I got from the relationship manager was that "it is with the head office" and when I asked how long it was take, it was always a "I can't give you an answer".  When I asked for a contact phone number, I was told that they did not have one.  So you can tell I was pretty pi$$ed at this point.

Finally, they submitted the documents to the LPI but not the notice of death.  A week later of no action, my solicitor decided to submit the notice of death herself to the LPI and then after further complaints made by me, the title deed was then reproduced.

Actual Question *******

At this point, I had absolutely no faith in HSBC anymore.  It wasn't really just the interest I accrued due to their delays but the poor service and lack of communication.

Today, I got quoted my discharge figure which was about $2K higher than I expected (after settlement fees etc).

I enquired with the relationship manager and got the same answers again (that's the figure they have, they don't know etc).

Basically, what has happened was that on the 27th Aug, we were debited $16xx interest which gave the loan a balance of $300K (for simplicity sake).  Today, my discharge figure was $300K + the full IO + P repayment of Aug + settlement fees bringing it up to about $304K as an example.   Wouldn't this mean that I paid interest twice as the full repayment of Aug would have an interest component included and I already had the Aug interest debited on the 27th.  The settlement team said this was correct and that's how it works.  Am I missing something here?