Who sells a product that dont work on your network

I have recently upgraded to a Sony Experia M4 Aqua LTE cellphone on contract with Telkom Mobile. I was assured by the coverage map and the salesperson that I will be able to use LTE with the phone. It didnt. I spent hours changing settings, even calling their helpline (which is always overloaded). So they drew up a case report, to check the signal here in lovely Cape Town (!!) So I called again after no one got back to me. They will make an appointment to come check my signal. While I was speaking to the person at the helpdesk, I thought there could be a problem with my phone. I asked about LTE and suddenly I was told that this model does not support the required Band/Frequency for Telkom Mobile LTE and I must buy an iPhone or Huawei 3G/LTE modem in order to make use of their LTE network. Excuse me, what? HOW is this not essential information when you sell someone a phone?? HOW DO YOU SELL A PHONE THAT DOES NOT WORK ON YOUR NETWORK??? Needless to say, I am furious and I want to return the phone.