Receive half your order

I bought two batteries from a company. Internet express was supposed to be the trusted courier firm. I get to the locker boxes and only one battery arrived. I enquired from both internet express and the company that sells the batteries. There was a enquiry number generated at internet express and after 21 messages between me and the agent she said that they just don’t know where the item is. I cannot just accept that I paid for something and it doesn’t arrive.