Missing payment FNB business account

I received proof of payment from a company we supply to and who we've received payment from numerous times, they sent us a proof of payment on 2020-04-08 which didn't reflect in our on account, i was then told that the missing payment department will investigate, eventually in June i was told that the money would be back in our business account in 14 days, this has till not happened! when i call i get taken back and forth to complaints departments with no solutions nor the money in our account, this is frustrating as we are a small business and we too have supplier to pay, this has been absolutely unacceptable