Late delivery of cellphone

On 30 June, I ordered a HTC One M8 from MTN store. They placed an order on 1 July. My phone would have been in store, the next week on 7 July, at the latest 10 July. On 7 July, no delivery. On Friday, still nothing. Calvin called the couriers earlier that morning. They told him that they couldn't tell him when their stock will arrive. This is now 15 July, and still no delivery. This is unacceptable. I do not have such a problem with the fact that the cellphone hasn't been delivered, but please if you are not even able to give my a date and time as to when it will arrive, then I blow my top.