Dual sim isnt actual a Dual sim

I am very disappointed with the service i received with mtn telephone upgrades.After i specifically asked for a phone with a Dual sim option i have been supp**** with one that has the second slot not working , only after receiving the device have i been notified that it is now gnome to supply it that way. Please note i would have never opted for a Dual sim if i didnt want to use both slots and to add insult to injury when i called the service centre to enquire i was told even if i am to change the phone i must not raise my hopes up theres a high chance even the one i will get will probably not work.This makes no sense to me as i have a dual sim phone previously and it has always worked with no issues .Is this how to treat good and paying clients?