Organic Designs fails to fit double glazing

We booked and paid a deposit for double glazing with Organic Designs of Diep River, Cape Town on 28th January 2015. <br> The contract states the following: \Lead time of manufacture / delivery: 15 - 25 working days from receipt of deposit & signed quotation"<br> We should have had our windows by the absolute latest 6th March 2015. Yet as at today 13th April - a further 25 working days later - we still don't have double glazing. The frames have been fitted and the job is half done.<br> I have texted"