Insistently Implying Order Fault Cause by Customer

Received call from Mr Delivery call agent stating order stating Kauai Capegate [VA], which is only listed one in Brackenfell, were unable to supply order as it was not listed on their menu. Immediately after this was stated, agent began to imply that I must have not "cleared my basket". I told him that i did not appreciate the implication, after all its only order i have made in two days and would obviously receive notice of anything in basket. Order was performed via app without any problem or faults occurring. But agent still imp**** yet again that it must have been customer fault. Thereby i immediately demanded order be cancelled and amount refunded. Had agent not insistently falsely imp**** customer fault, i would have simply ordered something else from Kauai. I clearly understood what call agent explained as fault, but since i followed all app steps when making order than the fault obviously lies on Mr Delivery's side. Also if item is not available at supplier than ensure app is updated accordingly or at least state new items may not be available at certain food branches. This has really frustrated me on a really hot day at work and unable to leave, as i have plenty of work to ensure is completed by end of day.