Charging for the services not performed

I called them to repair the alarm system. The technician after coming home told me that he does not know about this system and the manufacturer of that particular alalrm system is out of business, and there will not be any charge, he told me that I should call the office and swap for the new system. On the delivery ticket he also mentoned that there will be no charge. Now they are asking for the charges. I was without protection for several days. I explained to them but they do not want to listen to me. I am planning to report to Attorney General.