Extremely bad service on new facility application

I started an application with FNB in April 2019 to increase my one account facility. After a few complaints and plenty of follow-ups, I received an official offer from FNB on the 6 of September 2019. I can not really say why the big delay from the application to receiving the offer! Again after a lot of conversations and wrong paperwork at the lawers, we manage to get the new facility to some department in home loans, the 22 of January. Today is 6 of January and still no active facility. The most disturbing part is that I am paying interest on accounts that should have been closed by now, including the current one account. Apart from the enormous frustration and time spend on this application I want all interest paid back since September as I seriously don't think it should have taken longer than September to complete the implementation of the facility. I have raised various complaints but the resolution proses are useless!