Staff are uninformed

Was promised a interest rate of 7.8% on a investment by the staff. I have written proof in one of the staff members handwriting. I was told I cant go on what their brochure states as they have to manually put in the amount, time period etc and the system shows you the interest rate. I asked them over and over if it would show 7.8 % and they assured me it would. When I asked for proof they made a phone call to request a copy of the contract which would show the correct interest rate. 3 weeks later I notice on my banking portfolio the interst of 7.5 as per the brochure. . On visiting the bank the manager claims to ' not remember ' but the inetrest rate is definately 7.6.% In future I will only invest with Nedbank as there is total transparancy. Very disappointing. I am still waiting for a promised phone call from the regional manager.