Why tell me I will get my parcel today, if they can not deliver?

I was suppose to receive a parcel from Afrihost today, I got an SMS from RAM Couriers notifying me that my parcel will be delivered today between 9:00 and 17:00. so i took the day off as i do not work from a office or from home. It is now 18:00 and i have not received my parcel. I wasted a day that I could have worked due to them notifying me that i will receive my parcel today but then never showing up. I was at home the entire day and kept looking out the window every time I heard a car. I Tried to phone their offices before 17:00 here in East London and they do not answer.