Does Truss Mecca uses customers as scape goat for debt of others?

We are currently building a house in Clarens and contracted TRUSS MECCA, a division of the MECCA GROUP, in Phutadithjaba in the Eastern Free State through our builder to supply all roof related material to the value of R161 674.38. TRUSS MECCA issued us with an invoice via the builder with our name and building site as delivery address on 8 November 2017. This was paid for in full to the builder who on 9 November 2017 paid TRUSS MECCA on our behalf (We received bank transaction proof from the builder).The final deal agreed to between us and Truss Mecca was done through our Principle agent directly and not through the builder. We were offered a 5% discount by Truss Mecca if we pay the full amount immediately and not in the 2 stages that we wanted (the garage and flat first and then the main house when finished). TRUSS MECCA then could not deliver our specific order in December 2017 as promised, but instead offered us a different alternative not acceptable to us. We declined the offer. Truss Mecca then supp**** and installed half of our originally agreed order between January and March 2018, for the garage and flat, but now months later, refuses to supply the rest of the material for the main house due to the builder now being in arrears with his general account with them( an amount more or less similar in value to our outstanding roofing). One of the directors from the MECCA GROUP informed us per email via our Principle Agent to sort this out with the builder because they have no dealings with us. He said they will supply a new quote for material and labour at cost price, but the quote that we received from them now, is more or less the same as the previous one. Is this legal and fair from TRUSS MECCA/the MECCA GROUP to have this attitude and make us pay twice for the same material? The MECCA GROUP’s Core Value Statement on their official internet website clearly states that they see honesty, integrity and excellence as non-negiotiable. It also states that they will treat customers and suppliers fairly and will walk the extra mile. They claim to have an open door policy, but they do not even bother to speak to us directly or grant us an audience. I feel that we are being used by TRUSS MECCA as the scape goat for our builders’s bad debt! This ultimately means we have no choice but to pay Truss Mecca or another roofing company again if we want a roof over our heads.Where are the honesty, integrity and fairness in this?