FNB not paying what is due to us

My mother passed away a little over two years ago. She was a lifelong FNB customer and had appointed the FNB Fiduciary Services as administrators of her will (for a healthy 3% of the total value of her estate). Their service has been nothing short of abysmal. I had to do all the leg work in getting the relevant documentation together and as far as I can tell all they did was draft the documentation to place before the Master of the Court (something an individual can easily do themselves) and distribute the money. Approximately a year ago the bulk of the estate was distributed to the appointed beneficiaries. However, a substantial amount was withheld because the final tax assessment had not been done. This was over a year ago I have made dozens of phone calls and written numerous e-mails only to be completely ignored. I have not received a SINGLE response from Lynette Potgieter the individual dealing with the estate, she either just cancels my phone calls or ignores my e-mails. I contacted the FNB investment officer Wayne Aling who dealt with my mom's investments for many years. He initially tried to help but to no avail. As far as I am concerned they are *****ing our money. My advice is stay far away from this FNB service, it is absolutely pathetic.