Builder Warehouse - pathetic communication!

My partner, Mrs M M Nieuwoudt, placed an order for a 2 x Mobi-Volt Micro 5000w power inverter on 5th January 2026, and I , Mr D Muir, placed an order for the same item and the same quantity the next day. Initially, the Builders Warehouse website indicated that our orders would be delivered in 9-11 days, therefore both should have been delivered by 17th January 2026. On 16th January 2026 we received 1 each of the two that were ordered. Logic dictates that all 4 items should have been delivered at the same time, given that i live in a rural area. Subsequent communication with Builders Warehouse has not provided any rsolution, besides "escalating the matter" regarding the outstanding items. In fact, we are being ignored. I have subsequently heard through the g****-vine that they were accepting orders for an out-of-stock item. Who is collecting interest on the amount that was paid over?