Please pay what you owe

Innovation Group claims department authorised a claim on 30 August 2017 but never paid. Apparently there was an error in the way we made out the invoice but they never communicated to us that they would not pay out unless we corrected the invoice - they simply just did not pay. Non-payment went unnoticed because IG can take between weeks and months to pay claims. We only found out about the error because we phoned them to find out why they did not pay. We have since spoken to various people over the telephone numerous times and sent emails. We issued a new invoice as per IG's instruction but then they would not pay because they wanted to know why we were only invoicing the claim now. Again at IG's instruction we wrote and sent a letter explaining the whole situation. Every time there is an automated e-mail response but no communication from an actual person. I phoned again a week ago and was referred to a specific administrator who, I was promised, would help me. We still have had no response. I phoned again this morning and was passed from one department to another, still with no success of speaking to anyone who has actually helped to resolve the matter. We did the work and deserve to be paid. For a small business like ours, not getting paid - even seemingly small amounts - negatively affects our cash flow and daily operations. IG brags about how big they are and work with hundreds of thousands of Rand daily. Surely they can pay us the measly less than R3,500- they owe us.