Shocking payout

We have a client that had an accident with his trailer. He has insurance at Alexander Forbes. We provided a quote that was accepted after items were not covered by the assessor. We agreed and we got the go ahead to continue with repairs. Our quotes clearly state "Once accepted, please fax a copy of this signed quote, together with proof of your full payment and your VAT number" We started with the repairs as this is a good client and he required his trailer urgently. We advised Alexander Forbes on the 11th of April that the trailer is complete and we require the payment asap. 13/04 We spoke to Koketso and she advised awaiting authorization. 19/04 We sent her an email, she responded payment should reflect 26th or 29th of April. We referred to our quote that was accepted with our conditions, she in turn referred to their authorization. So in other words because they have the monopoly we should just accept when they are ready to pay? Once again we referred to our T&C's. It was ignored, however was read! 22nd of April we followed up on payment, was read again but ignored. 25th of April we phoned Koketso and left a message, no returned call from her. 26th we sent another email wanting to know if they treat their client this way and if we will be receiving our payment. Again was promised payment will be made as promised. By the 28th no payment received. According to Koketso the payment was not out, but will follow up with finance. Koketso sent me an email from the finance department advising that the banking details are incorrect and they require proof . We again sent an email explaining exactly how shocking their service is, why wait so long to advise that they are not happy with the banking details, we cc'd Koketso's manager Riana Durr. She rep**** requesting Adel Kotze to assist. 4th of May we had to email Adel for feedback, she advise that payment should be released this Friday (6th of May) and stated they have 30 days to pay. We once again explained our situation and that we are not a large company able to carry everyone's accounts till they want to pay. And guess what no reply. In other words "It is our way or no way" this is ridiculous.