Disgusting and Pathetic Service and Infrastructure

I requested a quote for a pc, business office software, mouse, carry bag.They could only provide a proforma and the company accountant was unable to make payment as they needed invoice. The wrong invoice was sent and payment was made. I went to the store after three days since payment date. When I arrived there they told me they have no evidence payment was made and no one informed them. They called the store manager and he had no recollection of anything. They questioned me on the person who sent the invoice and surely i don't know as I don't deal with company finances. I forwarded them proof payment & even then they were unable to reserve the products as they gave me quote on a laptop they did not stock. That is utterly disgusting and unprofessional, not to mention that I have work to complete and deadlines. Due to computer mania and their inadequate service and infrastructure I have renegotiate my deadlines for work as I can't complete it as I don't have the resources that they claimed they have. When I questioned delivery as I came through on my expense they told me I will have to pay out of my own pocket and wait till they can see if they can find one.They have no credibility!