Terrible Suppliers

I ordered my lockers and paid a deposit of 50% on the 21 April 2016 and my lockers was suppose to be delivered on the 29th April 2016 and they did not deliver or phone to say that they are not delivering after numerous calls and e-mails I got a mail back from Steph de Jager and was promised that the lockers will be delivered on Monday between 11 and 12 o'clock. After I informed her that Monday was a public holiday I was e-mailed again and told that they will be delivering between 11 and 12 o'clock today 3 May 2016. In writing I told her that my students will be arriving on Monday and can not stay with out lockers because where will they unpack. NOW it is 16:30 I can not get hold of them on their telephone or cell phone number and they are not replying to my e-mails and my lockers still have not been delivered. What do you call this? What does the consumer board have to say about suppliers that take your money but not deliver when their are suppose to deliver. What happens if a loose my student contract because I do not have lockers for these student to unpack their luggage - can I sue?