Asked for 50% and 50% after completing the job.

I went to Apex glass for a Quotation and found out how this will happen if I agree on the Quote. Spoke to a lady Belinda and was told that a 50% is required and 50% after the job is completed, both the shower doors and the aluminum. The shower doors was completely incorrect and now Apex (Paul) is demanding for the another 50% without the completing the Job, or threatening to cancel the Shower doors.<br> We here in life as consumers expect that the companies remain and keep to there word, how sure are we that they can do the job or not. Are they going to steel our monies and not complete the job. <br> Hello Peter please help cause I need done what was promised to me and the other 50% will be paid in full.