No response,lack of service and non payment

I'm overall a very relaxed and easy going person,so it takes allot to get on my nerve. To date it has almost been 3 weeks since two of our invoices has been submitted for claims made.Please note that both invoices contains exactly the same banking details.Now here is where it gets frustrating,they are willing to pay out the one invoice but the other invoice they can not pay out because they need to update the banking details<br> I've provided them again with the proof of banking details,receiving confirmation via email that all is in order and has been forwarded to management.Last week I phoned,asking whats happening with payment,lady said she would phone me back,still awaiting the call.Today I phone again,again they inform me that they are waiting for banking details to be uploaded onto system.Lady again tells me that she would phone me back before the end of the day,and again I'm still awaiting the call.This is getting frustrating,and will result in us refusing to assist clients with innovation warranties.If the outstanding amounts does not reflect in our account by tommorrow,then I am forced to demand that clients settle outstanding invoices.