FNB blocks business account with no investigation

My partner who is the owner of Wrought Iron Crafts Pty LTD who has a business account with FNB who have put a block on the account due to a unhappy client that informed the bank that they never got goods they paid for, firstly FNB did not ever incestigate the matter they simply found the clients complaint to be true and without any form of notification the account was blocked. My partner called all the numbers FNB have but it's now almost a year later and each month the facility and banking fees are deducted R377.00 so the funds in the account at the time of when it was blocked was over R8000.00 now there is just under R4000.00. We finally got an email saying we should contact the complainant and have there bank forward FNB a letter instructing FNB to remove the hold as the matter was sorted out. The client who complained works and lives abroad and is only home once a year and this means we are fuc*ed until the complainant returns. My partner has been running a legitimate business for over 5 year with no complaints and has been banking with FNB since 2013 but this loyalty and proven track record seems to mean nothing to FNB. Please can someone help us we have lost so much not being able to use our bank account and this we should be reimbursed for and all our fund repaid. Help my partner if you can we are not a giant company like FNB someone come save us please.