Upgrade Approved but still no phone

I have app**** to have my phone upgraded. I got it approved by credit vetting department, and the approved it. So the store tells me to come in and collect the phone, just to be told, sorry they cannot there is still one step that the back office needs to do. They will sort it out, and I can come tomorrow to pick up the phone. Been trying to email and phone the shop whole day. No response! Went through the call centre, everything is fine. Got an email from the store again,....\sorry still a back office thing\". I am so furious I think they can keep their phone. 2 stories, and still no phone."