no stock for weeks. utterly bad service

I have been trying to upgrade my cellphone contract for 3 weeks, phoned customer service they can't help i need to go to the store ,went in with all the required paper work, they then said that they can't process the application as they don't have any samsung s6's in stock. They said that they will give me a call on Thursday as they are to receive stock on that day. I had to call them. I lodged a complaint with customer service. They said i must send my details to another email they will be able to help with the upgrade. I am still waiting for someone to assist. Phoned the store again today still no stock they said i must phone customer service. When you phone them they refers you to the nearest store... this is utterly bad service. How can you advertise a product and not supply your stores with it?